Exhaust Leak with Greddy?
 

Alright, well I installed my Greddy SP2 exhaust along with my RP High-Flow cat, and I've noticed some "rattling" sounds from the exhaust every now and then. At around 4k, the exhaust note sounds different and it sounds really bad as if it's rattling. I'm debating if it is a exhaust leak which is leading to this sound. Where should I go for someone to check the car out? Should I go to a Midas or a local performance shop in order for them to check it out really quick or what should I do?

Anyone else have this kind of problem?

I thought someone else was having a similar problem with their RP Supercat. Once they had a hanger installed, the problem was fixed.

Exhaust leaks sound like someone making farting noises with their mouth.
Rattles are something else.

Right... one guy had the sound minimized by the hanger... another one had to get a resonator installed because the buzzing from the new cat, and another had an exhaust leak because the flange didn't line up between the cat and the end pipe and had to have a muffler shop do some work to silence it.

... so I would say it's definitely something with the RP cat, as I haven't heard anyone complain about the Greddy exhaust not sealing properly (including myself).

Went to a shop today, guy said it was just the way the exhaust sounds, it's the resonation from 4-5k is when it changes resonation and that's why it makes that sound. Anyone agree?

I'm not sure what rattling you hear but if you're hearing it above 4k rpms, then the hanger won't fix it at all. I had a NASTY buzzing sound around that rpm depending on throttle position, and it was caused by a leak. I had the local Meineke fix the leak when they put the hanger on and the nasty buzzing went away.

ps. It's definitely not the exhaust, it's the way the midpipe seals to the exhaust. I think since you reuse the stock seal it leaves a little gap. The muffler shop said they used some copper seal and it sealed right up. I don't know what the stuff is but they swear by it.

Copper seal? Are you able to get that from a Kragen or something and it's just a sealant that goes around where the downpipe and midpipe connect? I think I saw something like that.

I'm not sure where you can it, but I would imagine an autoparts store would carry it. I've never looked though.