1993 350 TBI sputter when down shifting.

[1993swb]

Ive got a 1993 swb with a 350 that has shorty headers, police ecm and injectors, and cold air intake. Runs and drives great. However when cruising about 50-55 and you really get after it it downshifts perfectly and revs to about 5500---6000 and gets up hard for a about 10mph gain then almost acts like it has a small sputter. Replaced spark plugs and swapped out the stock coil for an MSD street fire coil. But still has this issue. Anybody have any ideas why its doing this?

 

[STEBS]

does it register a check engine light?

sounds to me like spark advance, but thats just a shot in the dark...

 

[DRAGGIN95]

OK you say police chip, but is this chip matched to the engine like a custom chip need's to be?