Is this sound normal from LT's and a Borla catback?
 

I currently have LPP long tube headers and a Borla adjustable catback. I just recently removed my two mini-cats from my Y-pipe and am noticing a strange sound coming from under the car in the 2500 - 4000 RPM range when under load. Again what I am hearing is coming from under the car.

Its a light rattling almost raspy sound and it must be exhaust pipe related I never heard this sound when the cats were on and nothing else has been changed. I have been under the car and everything is tightened up and the pipes are not hitting anything. The sound is very annoying.

Is this a normal sound to expect from running long tubes, without cats and a Borla exhaust?

the spot right under the drivers seat where the y-pipe has a flat spot and goes under the frame i have pace setters and ran slp loud mouth but i think most kits are simalar in that spot my buddys cars made alot of noise and so does mine its something these cars do make all kinds of fun noises i just gave up on that stuff and live with it but chech that spot tends to be the trouble spot

When I used to run a Borla and off road y pipe with my LTs, it had a raspy area from 22-2800 or somewhere in that rpm range. This was when my car just had bolt ons.

When I got my first heads and cam setup, that raspyness got really bad and it sounded like shit. I ditched the Borla for a Magnaflow and it sounded good.

I have ruled out all possible vibrations and possibility of pipes banging something. Nothing there.

Fergy,
My noise is in that range too and usually when under light to moderate load.

When you heard the noise, did it sound like it was coming out the bottom of the car?

Did it have a rhythmic sound that had a distinct pattern?

Misfire? When I bruned a plug wire the car had a goofy noise at idle.

Dont really think so. It is running awfully well plus I got a dyno tune just two weeks ago and that would have beed noticed. But I will check the wires just to be sure.

I would just ditch the Borla and try another exhaust that is chambered.

What other catbacks are chambered?

My noise was just exhaust noise. It wasn't anything making contact or vibrating off something else. It just got a really crappy tone to it after the heads/cam setup. It sounded great with just bolt ons for the most part, other than the small raspy area.

I am now convinced that it is simply exhaust noise. When the cutout is closed it has the muffles machine gun sound and if you open the cutout it is the loud machine gun sound. Both sounds have the same pattern.

I am waiting for a local exhaust shop to get me a quote on doing mandral bent trual duals with a full size single dynomax x flow muffler out to the tips. If it ends up being an arm and a leg, I might get the Magnaflow catback since most claim it has no rasp.

Flowmaster, Hooker. I was told to stay away from bullet styles like SLP LM's. Go to Jegs or Summit and just browse through the catback section and just narrow your search down by clicking on chambered mufflers.

check your O2 sensors, they can break and rattle