Running a little rich - 1988 760 turbo

[gwoiler]

This 760 turbo wagon has been sitting about a year since it overheated. It uses a small amount of water. So I needed to use it so I replaced the fuel pressure regulator, the temp senser in the head for the fuel system, and thge air mass sensor. It is still runing just a little rich. It runs better in turbo with the vacuum line off the fuel pressure regulator. this means it is richer at idle mut leaner in boost sith the vacuum line off. So, what to do? How do I adjust the Air Mass Meter? Which way on the adjustment is leaner and richer? What elase could cause it to run rich? The O2 sensor was replaced a few years ago. I will do the head gasket in a few months. The engine has about 300,000 miles and only leaks oil out the rear main seal. Any suggestions are appreciated.

Oh... Even though I had replaced the temp unit in the airbox the last time I replaced the Air Mass Meter... (2 years ago) it was bad upon inspection. So I jury rigged the flap so it can NEVER channel preheated air in to the box now.