Need a little help please. A neighbor pulled the motor out of his 89 Camaro RS and had a local machine shop rebuild it.
89 RS TBI 305 A4. His request to the shop was a 100% stock rebuild. We found out later that the shop cut the heads and installed 2.02 valves and roller tip rockers. No idea why. He does want a little more power but for the most part this is a daily driver. We installed Edelbrock TES headers and Y, High flow cat and flow master catback as the only planned mods.

The issue is that I only have 16 inch vac at idle and is way to rich. Will never pass emissions test. I put a hand vac pump on the MAP and pulled it to 20 inches vac and the idle improves and we not longer have the black smoke out of the tail pipes.

Any idea what vac should be at idle? I have gone over every thing I can think of. Verified that we dont have any vaccum leaks, Everything seams to be connected right. Have moved base timing from 0 to 8 deg adv and 16 inch is the best vac reading I can get.

Any ideas what to try next?

Any input is appreciated.