I found one of those little black "cap" things -whatever it is.. lying between runners of my UIM! (2.5 ATX) Have no idea what it is or is supposed to do either. Currently in the change tray of my dash -waiting for somebody to identify it. Car runs great with/out it attached to anything. Couldn't fin any reference in Haynes either. Maybe part of ABS/TCC? -I've had CEL's on that. As for your idle problem.. Take off the TB and check that the EGR ports are clear - mine were plugged with black crud and had similar prob. Clean-out with solvent and air and works fine now.
