i've had both kinetix and ultimate cats on my car, and both have made this really annoyin sound when deceleratin in gear. it sounds like someone tryin to whistle with their teeth together. the sound isn't there when my stock cats r on though, so i don't it's a gasket or anything. multiple shops have looked at my exhaust, too. i think i'm at the point where i'm gonna just put my stock cats back on, take that $800 in the ****, and stop chasin the dream by goin further in debt tryin other cats. this sucks.

 

Two different sets of high flow cats do that? sounds kinda fishy if you ask me.. Did you have the muffler shop do a smoke test for leaks? It could be that since your exhaust is now more free flowing it is starting make the Borla show it's greatest weakness--leaks!

I have the UR cats on my car and there is never any whistle noise..

--mike

 

I think you are experiencing the "hiss" that is common among many members who have resonated test pipes, or even high flow cats. My crawford HFC eliminate most of that noise, but i still get a slight hiss at around 2500-3000 rpms on decel.

 

yup i get a hiss too with megan pipes kinetix pipes and now my Ultimate HFC its normal comeswith the terretory i guess but it does suck

 

its way more pronounced with testpipes, tho. barely noticable with my crawford hfc. i actually liked the sound...kinda lika mini purge sound, but i hated the gas smell with the pipes.

 

yea i have the crawford cats i do hear that swooshing sound during decel when parked and reving up over 3000rpm. i don't hear it when im driving. I heard its the resonance on cats due to higher air flow.

listen to it carefully is this the sound you guys are having too sounds like a mini waste gate:
http://members.dslextreme.com/users/g35driver/noise.wmv

 

wanna sell the ultimate cats?

 

lol. i don't know what i'm gonna do; it does feel good to know others have this issue though. i need someone to drive my car around a parkin lot or something, so i can hear it from outside the car. i'm more worried about that.