I have an 88 Mustang LX hatchback 5-speed. I recently
put in a GT-40 Crate engine in it with 345hp B-303 cam
(I know that is overrated. It runs real strong. I also
put a off-road H-pipe,big tube
shorty headers, Ford underdrive pulley's, Cobra
intake, 24lb Ford injectors, cold air intake, 65mm
throttle body, PMA 75 mass air sensor calibrated for
24lb injectors, stock computer. The car has a real
rich idle. What can you do to get rid of the rich
idle?

 

whats your fuel pressure at? Im not 100% sure but i think a vacume leak can cause it to run rich also

 

I have a e cam and I was running rich too but now I have the Air Adjuster from IST and it seems to work for me. I don't have it dialed in yet for fear of leaning it out but it is much better than it was.Apparentlythe B303 and E303 are known too run rich due to improved airflow through the engine.http://www.mass-air.com/Products.htm

 

could also be the type / brand of mass air chosen and it's "Calibration" factor