Odd Noise Upon Acceleration
 

I recently installed a complete exhaust system on my 95 v-6. I have MAC shorties and catted h-pipe, with a flowmaster american thunder muffler system. The problem I have is that upon acceleration, I have a really loud airy, almost metallic type noise. It is what I would call raspy, but for some reason I think that my definition of raspy may be different than others (that's a shot at those that think flowmasters on a 6 sound "raspy"-I had flows on before this new setup as well and I get is a nice deep, smooth sound from the mufflers throughout the rpm range).

Back to the issue...

It sounds like a really large exhaust leak, but I have taken things about and put back together many times, tightened everything as tight as I can possibly get them, and have sprayed soap/water on each connection, only to find no leaks. I know it is not the headers because I had to install the h-pipe/mufflers before I received the headers and the noise was present then with the stock manifolds. Every sound clip I can find of a 6 has no noise like this. Has anyone seen/heard of anything like this? It can only be heard when under load. Under light pedal, like steady driving, you can't hear, but when you mash the gas it is there.

I tried to explain the best I could. I know a sound clip would help, but right now I have no way of capturing one. Your thoughts....?

Scott

Huh..sounds like your flux capacitor might be going bad lol jk

Sounds like an exhaust leak to me.

does it make this sound in the high rpms also?

Not that I can tell. The mufflers get kind of loud around 2500-redline, but it does seem to fade up top.

See, and that's why I have taken everything off several times in the past 2 weeks or so, but to create this type of noise, and as loud as it is, it would have to be a MAJOR leak and there is nothing that I can find. My GT has a leak at the passenger collector, but it has the distinct tick tick when giving it gas and can only be heard from inside the car with the windows up and the radio off.

Is it possible the EGR tube might be cracked open?

Well, I did not take the tube all the way off (only disconnected from the manifold and attached to the header) when I did the headers and the fact remains that the noise wasn't present in stock form.

Here is a theory that I am going to explore later as soon as I get the chance. I was looking at it tonight and it does appear that on the passenger side, the downpipe is at slight angle where it attaches to the catalytic converter/h-pipe part of the system (Header>Flange>Downpipe>Flange>catalytic converter and h-pipe>Flange>Muffler and tailpipe). My theory is that maybe the connection is opening up when the engine torques, since the noise is only present at medium to heavy load and passes the soap and water leak test at idle. Hopefully I can work on it here in the next day or 2. I mean, I noticed that the connection wasn't perfect, but I had those nuts as tight as I could get them, so I figured it would be ok.

Thanks for the help. Keep the possibilities coming. I'll post back with what I come up with.