Flys_Lo

I have a 99 GT vert', 40k, 5sp. I replaced the factory exhaust two weeks ago with Flowmaster 3 chambers and a BBK off-road X pipe. I'm happy with the sound at idle but when accelerating through the gears it gets very raspy - exhaust leak raspy. I've checked for leaks, re-tightened, re-installed, and it's still raspy. It sounds so bad that I'm ready to ebay the whole system. What did I do wrong? Is it the BBK? I know it's cheap and I bought it because I didn't think there could be that much difference in just straight through pipes (no-cats). I'm going to fix this problem no matter what - so give me advice on what to do/buy please!

Dan04COBRA

It's your Flowmasters.

Chambered mufflers are not friendly with off-road midpipes.

Flys_Lo

Okay - I see you have a similar setup but with the MAC's. How's your's sound? I guess I should do a search to see what others are using with the O/R pipes. I'm not looking for the loudest car out there, but I do want a good, deep growl. Anyone want a Flowmaster cat-back with 60 miles on it?

sowaxeman

Sounds to me like it would be a good idea to use the same manufacturer all the way back. I did a complete MAC system on my 93 (5.0 vs 4.6 of course) and I was very happy with the sound. Not sure I would ever mix manufacturer's in this scenario for fear of them not being properly tuned for each other.

Dan04COBRA

Being properly tuned for eachother has nothing to do with it.

Higher HP cars with baffled mufflers and no cats simply do not mix. The only remedy for it would be to increase the distance from your manifolds to your Flowmasters other than putting a set of cats back on.

Mine sounds great at 1/4 throttle, no raspiness, nice and smooth. Go anymore than 1/4 throttle and it sounds like it will blow the baffles right out.

94Cbra

I had a 1996 GT with an off-road X and the A/T catback. It was raspy under hard throttle but it wasnt severe. Must be a 4.6 problem because they sound amazing on my 5.0 .

Flys_Lo

Thanks again Dan -

I've got the same 1/4 throttle breaking point.

Looks like my options are:

1. Put cats back on...
2. Replace FMasters with a non-baffled system.

Reinstalling cats seems like a step backwards in performance. I'll start researching cat-backs without baffles - do you know of or have any suggestions?

Djs94stang

I'm probably in the minority here...but I think a street car sounds better with cats....either that or a magnaflow/ultraflow muffler with some packing to get rid of the rasp.

Dan04COBRA

You should look into some high-flow cats, you'll PAY for them definitely, but it'll solve the rattle problem and todays high-flow cats steal 0 HP. Plus, you'll be emissions friendly.

I'm thinking about buying 2 cats or a set of Dynomax's...

Albizo66

The combining of different exhaust company's pipes idea is wrong. I have MAC longtubes, BBK O/R H pipe, and SLP Loudmouth..and there are no weird sounds or anything..its actually perfect..I get the sound I want, the power I want..maybe I just got lucky, not sure..But you guys are killing me talking about buying cats..damn guys come on

Also, the raspy sound..is that the trademark X pipe sound raspy while the h pipe is the deep classic muscle car sound? That's what I always thought..