Dry hop I don't want to make you sound "small" at this time but didn't you see what I said!?! I said you need the z6 intake maninfold, it is diferent you ARE GOING TO GET A VACCUUM LEAK! I tried it, too. Again, yes you are going to have the idle fluctuate with it leaking.

no the gasket is not going to help, no tightening the intake manifold bolts is not going to help. try this: take out your intake and cover your throttlebody with your hand, hear for the hissing noise, to confim this is part of your culprit.

If that is not your problem try check the iacv valve behind your intake manifold.

Not that you got to play with your fields controller and tune much better, richer.

When done with that play with the idle screw on the throttle body, it's brass with a flat head screw driver.

You got to tell me how the car runs, drives etc. so I can help you more.

What ecu are you using?