I have a vacuum leak that I can't find. I get a 25% lean condition on the passengers side 02 when I'm in a low engine load or off pedal driving situations. I noticed (w/HP Tuner VCM scanner) that the issue is very noticeable (the O2's go in opposite directions) if I'm going down the road and lift off the gas and put the car in neutral I'm getting air from somewhere on the right side bank of the motor.

The heads are milled (not sure if they angled or not or both) .040.

Question...if my intake is not fastened to the heads perfectly due the heads being milled this much could this be my issue with the lean condition on 1 bank of cylinders? I can't find a vacuum leak anywhere, sprayed carb cleaner all around the intake and ZERO happens.

Can this be the issue and if so, can I mill the intake to match the heads some how to get rid of this problem?

 

I'd like to know too. I think it could be a good chance especially if they weren't milled flat.