Hey guys/gals, I got the A6 all together save for the bumper and it runs great, except for one thing. When the engine is at idle, and I blip the throttle, something at approximately the center of the right bank rattles until the revs go above, lets say...1100. I get the same rattle if letting the clutch out at a low speed coast (bogs the engine just a bit). The check engine hasn't come on in 20-30 mintutes of running so I'm out of ideas. I've about 95% eliminated anything in the radiator support, fenders, etc. Any ideas are welcome.

I'm quite sure that the sound comes from the broken (inside) exhaust manifold. It's typical fault in those engines. I'm having the same problem and i'm going to build new manifolds by myself.