on my 89 350 tbi, its over fuelling itself. absolutely all sensors are up to specifications, and the motor is new with vortec heads on it. all scanner data is good except for my map sensor readings. The engine vacuum is up to 17-18 in. but the scanner map data is showing 9 in. at idle. even tried vac test at map sensor and its showing good vac, but not according to the scanner. tried a couple I had laying around here and still get the same readings. any ideas??

 

You left a lot of information out of your question. injector size , If you have a different prom ?
Does your scanner show kpa ? With 17-19 I hg you should see 60-65kpa.
Is your cts reading accurate ?
tps accurate
Is this occurring in open and closed loop ?