Some have mentioned a grinding noise after installing a 3in turboback exhaust. It sounds as if the exhaust is touching the rear drive shaft. But it's not since there is a big clearance bewteen the exhaust pipe and the drive shaft.
What you are hearing is the down pipe rattling against the frame or some part of the car. It is a slight touch during acceleration but there is so much vibration it sounds just like a grinding noise. There isn't much space for any 3in DP. If you didn't know you installed a 3in DP, you would have thought the clutch was going bad.
So the drive shaft will not touch any exhaust but the 3in DP will touch somewhere if the tolerance is off by just a fraction. I just got a DP and learned this. I will post that one later.

just my .05 cents

 

Going along with that, being one of the few Lancer owners with a Buschur downpipe which easily eclipses the stock downpipe diameter, you will here the pipe clang if the engine shudders to much from something like a bad shift or letting the engine shudder and bog down a bit.

 

my downpipe hits something down there at exactly 950 rpms... probly some form of heat shield i don't know, i gotta check it out next time i get a chance to jack up the car.

i have the vishnu btw, but i don't think i've heard of anyone else's doing that, so its probly something i did wrong.

 

It cloud be hitting the tie bar or it might be hitting the upper cross frame that connects the two lower axle arms. Mine was hitting that one and made grinding noise. Easy way to find out is when you are under the car, push the downpipe up; and if it hits without moving much, that's where it's hitting.