OK, this may sound weird but some time ago I read of a problem like this and it turned out to be the rubber bellows attached to the intake were collapsing under higher rpm and restricting airflow. The symptoms were exactly as you described. Check that out before you start replacing things.

 

I first noticed my problem when i got my tuned pcm. So maybe it does have something to do with the wire that runs from the pcm to the IAT or the PCM itself. Like i said my car ran fine last night with the IAT unplugged until my SES came on. I'm going to try the IAT resistor mod and see if that works.

 

Blaze309, let us know if it helped.....
Did you try loading the original PCM s/w back?

 

had the exact same problem. turned out fuel pump was running out of steam around 4500-up. F'n fuel pump

 

mohawkmike,
New problem was added, it was also miss firing in low RPM (below 2000)
I went ahead and bought a fuel pressure gauge and tested pressue. Guess what, it was 20PSI under load and 30 in idle.
Changed filter, checked regulator and eventually changed the fuel pump (accel) car is back to perfect. no hesitation, no miss fire and it pulls like crazy.

Thank you all