I have a greddy evo 2 exhaust and UTR hi flow Cats and the exhaust gaskets blew. I swapped the gaskets out for some form autozone and now the exhaust sound is way quiet? Is this possible or did something happen to my UTR cats? I thought I knew how exhaust systems work so any ideas would be great. Thanks

 

Is the exhaust very quiet compared to stock, or very quiet compared to what you were used to? It might be that the gaskets were never sealing properly and you essentially had leaks, which could allow a lot more exhaust noise. Now maybe the sound is exactly what it should be. Is there anyone else in your area with the same exhaust so you can compare?

 

you know ,,,this could be very true !!
when i first install my HFC there was a very high RASP i thought its ok as i read in here ,but when i checked my installation there was 5 bolts are not tight ,,,, the RASP now 50% quieter than befor and the exhaust much better deeper sound .

 

And depending on the size and where the leak is, it could have caused the loss of TQ you reported.

 

Sounds like you had a leak originally. Now you sealed up the system and things quieted down. I have seen this several time before. Basically, I never reuse gaskets. I always end up with a leak so I stopped trying to save a few bucks. Just buy new ones if you're going to open up the exhaust. I don't know if you reused originally, but if you did, there was a good chance that was your problem.

 

No, the exhasut is actually as quiet as the stock exhaust. I installed all new gaskets that came with the Greddy exhaust, origanally. However, my thinking was that the new gaskets I used to replace the Greddy ones are from Autozone and have alittle (.125 inch) diameter difference. Could this little difference interfere with the sound?

 

Was is .125" too large or too small?

Probably didn't make a difference anyways.

 

is that possible it was not that loud ,well the lose bolts 4 of them wear in the Heads/HFC gaskets ,but really i gained some Trq back waiting to dayno and see the gain .

and about the Greedy going quieter than stock
we need a clip man

 

well I don't have a clip from before but I would post an after clip if I had a camera or anything that could record sound. I know it sounds ridiculous and thats why I thought maybe it was just me being paranoid but after many (4) people agreed I thought I asked. The .125 difference was smaller. Would that create turbulence but wouldn't that make it louder?