I bought my Evo 8 with an HKS Hi Power Exhaust already installed. I noticed a strange slight vibration/soft/rapid clunking/rattling at idle or very low rpms. It sounds like an exhaust pipe hitting something. Which I am pretty sure it is...

Today I was changing my oil and inspected the TBE. Sure enough, there are marks on the exhaust resonator right next to the driveshaft where it couples in the middle with tha carrier/bracket.

It also seems to surface when the A/C is on. This could be separate issue, just the A/C switching on/off and/or not bumping up the idle quite enough to prevent this.

My first thought was that the exhaust was moving around too much, however, it appears to be pretty taut in its location and not particularly out of line fro where it should be stock (I have no frame of reference here, as I've never seen it stock). On the contrary, it seems as if the driveshaft were actually moving over to hit the exhaust. Is there anything I can do, short of replacing the exhaust with a different design, if the other design even has the resonator placed elsewhere/not at all? More rigid driveshaft carrier bushings?

 

Well it is possible that it's installed incorrectly. Try loosening (but not removing) a few of the bolts and clamps, then try to get it into the right position and tighten them back down.

 

i assume you are talking about the exhast, right?