I installed the stage 3 system (minus the MAF Housing which is on its way). Anyway, the first time I put it together I didn't get the sensor on the TB right so I ripped it back apart tonight reset the sensor and carefully put everything back together. I'm not sure if the sensor setting was the problem or if I hadn't put it together completely right the first time, but WOW, the car is a kick in the pants to drive now! I can't wait to get the MAF housing on in a couple of days. I'm still not sure about the sound. On hard acceleration it almost sounds like something is rattling or ticking - it has always had a sound like that but now it's more pronounced...any thoughts?
And thanks for the mods Mance!

Kent

could be your cats going bad.

A4 - The thought of an exhaust leak or a cracked pipe had crossed my mind - anyway to visually inspect for a bad cat?

use a rubber hammer, if when you hit it it rattles. The cat is gone.

Bad smells (rotten egg) can also be a sign of the cat going.

If you have one of those ross-tech systems or a vag tool, the A4's allow you to view the capacity of the cat.

I really only har it at WOT, but its always been there.

I've been involved with installing mods on (either before or after). And it's not been a recurring or frequently asked question here or at the 90 forum so I think it's far from typical tho perhaps not uncommon. I have no idea as to it's origin.

But exhaust leak, fan blade, hub, viscous pulley, AC clutch hub, power steering/water pump and pulley-to-engine-cover contact were a few of my initial thoughts.

You can also get torque, int. hp and a bunch of other things. They are totally wired up! even which cylinder is not burning correctly you can monitor!

Have an 98' A4 and i got all that information from it.