taws6

iTrader: (2)

Hmmm,
I have a GMMG muffler, and want to add LT, but I NEED to keep the CATS.
Will I still gain hp from the LTs even if I keep my CATS? If yes how much approx?

Thanks.

FastB

iTrader: (11)

Yes, you will still gain plenty of hp. A lot of people run long tubes with cats and see significant increases. I think you could expect anywhere from 10-20 hp gain.

taws6

iTrader: (2)

Thank you for your reply.

I cant use hi flow cats, do you mean stock cats?

ChocoTaco369

You can't use stock cats. You have to buy high flow cats. You can either buy a catted y-pipe from the same manufacturer as the LT's or you can buy your own cats and have a custom y-pipe made.

2_wacko

iTrader: (2)

I had Pacesetters, Texas Speed Catted Y Pipe with GMMG. You would not know a difference without the cats.

blown03mustang

you wont have near as much rasp with cats, but might lose 5hp at most. Yea id say its worth it, especially considering that gmmg is one of the "the" best sounding exhausts on the market

Summerwolf

iTrader: (3)

Yep most catted ypipes come with the appropriate highflow cats and bolt right up to the headers and the catback. You might lose a slight amount of HP using the cats, but it will be much better than stock

RevGTO

iTrader: (12)

It will be fine with aftermarket cats, and trust me, you don't want to run LT's & GMMG without them. The loudness and rasp are unbearable. Tried it and couldn't stand it for a day.

taws6

iTrader: (2)

Thanks for the help.

I just need to find out if I can use the hi flow cats, as I dont think they will pass our emmisions test.

I do know some friendly testers, but I will be moving abroad, and can't rely on friendly testers for long.

I will find out more about our emissions test.

Thanks again,

Paul.

DaSkinnyGuy

I passed my emission with high flow cats. They still get the job done for emissions. The high flow cats just flow the exhaust better while still getting good emisions. gets the longtubes, high flowcats that should come with the aftermarket y pipe you will get with your longtubes.

blown03mustang

i have heard the same thing from a few others....the high flow cats should work just fine

taws6

iTrader: (2)

I have spoke to a couple of testers, and they are not sure if the hi flows cats would pass emissions or not.

I can get the LT here really cheap, but the catted y is $$$$$$$ with shipping & taxes. Even a custom y isn't going to be cheap by the time I add the cats and labour. And it still might not pass our emissions.

Mabey I should just get a cutout. Would that gain me much hp over my current set up? (Stock header & y pipe and GMMG).

Thanks for all your input guys....

99_SS_LS1

iTrader: (4)

I don't know what your emissions standards are across the pond, but with the American racing LT, and catted-y (magnaflow cats i believe) I passed the emissions test, even with a misfire!

99_SS_LS1

iTrader: (4)

just realized i didn't explain that well... and I'm sure I'll get "flamed" for it

Michigan does not have emissions testing, I did it at a local college just for the hell of it