staringback05

iTrader: (8)

Im going to be putting together several input ideas from reviews of catback owners for later use.

right now i need GMMG catback owners only to post in here and give me there opinion's on their catbacks..

i will have other post for other exhaust systems later, so please fellas once again only post your reviews if your an owner and not debates, im gathering this for later....ill give it a few days then im going to ask a mod to lock it

thanks

Specialized

iTrader: (15)

I love (d) mine. Even with Lt's and ORY. Mine was kinda annoying rolling into about 2krpm through about 2800 and then anything after that screamed. At idle, it was loud but tolerable. You can easily drive around (if 6 speed) at night and not cause a total ruckus.

WeathermanShawn

iTrader: (1)

Hey Jacob:

While all exhaust sounds reviews are generally opinion, I'll try my best.

(I have also had a Borla cat-back system on a previous LS1.)

With stock manifolds I found this exhaust system fairly quiet, especially at idle. Too quiet. Under WOT it had a deeper tone, but overall I found it fairly mild.

With the addition of LT headers (with cats) it woke up. Still somewhat "quiet"' at idle, but under WOT it was obviously much louder, and had a more distinctive and somewhat deeper tone.

Adding cam/heads made this system live up to my expectations. Deep, throaty idle reminiscent of a bigger-block "old-school" muscle car. Nice deepening pitch/volume under WOT.

I have done cut-outs and Borla cat-back. I liked each of those exhaust systems in differing ways. With GMMG w/cats for me, the system needed the addition of headers & at least cam to reach the full potential of it's unique sound.

It's all subjective, but hopefully that will help.

Good luck..Shawn.

Demon Of Dreams

iTrader: (3)

My setup went from stock Manifolds/Cats/Catback to the stock Manifolds/Cats/GMMG and even then its a big difference, I love how it sounds...

when I do my LT's/ORY I have a feeling it'll get louder than I first intended, but I'll be throwing cats in later on down the road more than likely (when I do a custom Y setup instead of a pre-made Y)

I'm thrilled with it, had it on since February, and rarely ever listen to my stereo, it just sounds so much better than the stock catbacks ever could.

I can't wait to do my LTs/ORY and possibly even a cam in the near future

redtail2426

iTrader: (10)

i think its the best sounding exhaust for the ls1 f body personally.i have cats and the dynatech supermaxx system and it just sounds great.It has a nice smooth rumble under 2000 rpm,not too loud.But after 2k rpm you can just hear it come to life even at low throttle.At WOT it is loud but with a smooth high tech sound.Simply awesome and would recommend it to anyone.I have heard it doesnt sound nearly as good without cats though.

RevGTO

iTrader: (12)

I have it on manifolds/cats and it is plenty loud for me. It's quite a bit louder in the car when it's cold and the windows are rolled up - borderline too loud. It's great at WOT, but mild at light throttle and cruising once warm. NO DRONE at highways speeds - just a pleasant resonance. The sound has a nice deep tone that would become fuller and "rounder" with LT's, I'm sure. I like it, but at times I think of putting something quieter on the car.

staringback05

iTrader: (8)

thank you guys, keep them coming

Ramairbird

iTrader: (17)

I have mine with the dynatech header system and high flow cats. With the stock cats and manifolds it sounded good but but in my opinion under WOT was alittle quiet, Well now with the headers it sounds unbelievable. From the minute you twist the key to WOT the sound changed alot. It is not droaning or annoying at cruise, at idle it has a nice rumble to it and under hard accel it is very aggressive sounding but not so loud to get you in trouble. I couldn't believe how much the sound of the car improved with the headers with the GMMG. The only issue I had with the system was one of the rear hanger bracket welds broke, but it was several years after it was installed. I wouldn't change anything about it, great system.

2_wacko

iTrader: (2)

I love mine, sounds great with a catted y pipe and LTs. The things I had to modify was the tips, they hung a little low, and the mufflers rubbed against the gas tank.

SweeTbone

iTrader: (8)

Great catback. I had it on stock manifolds/cats for about 8 months, as it was great. Slapped on some Kooks and Kooks catted Y, and DAMN! Sounds absolutely stunning. Really deep tone with no rasp. WOT is LOUD & DEEP! At idle with LTs it is definitely noticeable over stock. I uploaded about 5 clips to http://video.ls1tech.com of my GMMG (Just search "GMMG"), both on stock manis and with LTs. One of the best mods I've ever done to any car I have ever owned.

Eiyse98ls1

ive had my gmmg for 2yrs now and love the sound... i curently have stock manifolds w/ cats... has somewhat stock sound at idle but above 2k it has a distinct sound. i recently added a ls6 intake and now at above 2200 it has a changed tone that got deeper sounds alot better, all the way to redline... im still debating on lt's as turbo may be a future upgrade.. as stated above i do not like the way the tips hang out back.. they hang low/ piont downwards.. other then thats its a great choice.. also did not do with the optional tips not sure if that would of made a change in tone at all. i had a friend that had the optional tips on his 01 ss w/ ypipe and the sound was a little deeper sounding then mines.

bob320fa

My experience has been mixed. I initially had a lot of fitment issues but, whether it was the system or, the installer I'm not sure. I took it to a second shop and they tweaked it perfectly.
It has a much tamer volume on the stock manifolds than I expected but, whether it's my imagination or not, it seems to be getting louder with some mileage on it. I can't wait to see what long tubes will do to it.
As far as tone, it sounds great even on the manifolds. Once again, can't wait for the tubes.
The one piece of advice I would give anyone looking into a GMMG is, don't waste your money on the "premium" oval tips. For $150 they're crap in my opinion. When I can get around to it I'm putting my corsa clones back on.

gollum

iTrader: (1)

Over time the GMMG exhaust tips will hang lower on the drivers side...you must bend brackets to adjust. I have mixed thoughts on sound quality with long tubes.

Justin00SS

iTrader: (5)

My buddy's 408 trans-am sounds GREAT with the GMMG.

Nate81Camaro

^^^Didn't he ask "GMMG owners only" ???

97RedZ28's GMMG cat-back sounds delicious! His exhaust is stock between the manifolds to the GMMG, but he has Pacesetter LT's to install once he gets back from Spain.

It sounds really nice, I'm very impressed!

Finite1

iTrader: (3)

Ive had the system for a few months now. I searched long and listened hard to make sure thats what I wanted. and Its a great system. I'm very pleased with the sound and performance. The quality is top notch. Standard tips here and its welded.

My only issue is the system vibration occassionally hits under the car making some unpleasant banging. We removed the heat shield and that has helped quite a bit.

It really doesn't look like the garage failed, the welds and everything looks good and even. I think if it was adjusted lower it wouldn't look right. So maybe others had a similar problem.

But yeah GMMG exhaust is REAL nice. I love it.

Eiyse98ls1

as mentioned above yea it did also seem to get louder as more miles get put on it.. also did noticed it got louder after i took it to the track.. i do also feel more vibration from the system buts thats ok as long as i know whats causing it..