NO misfire But Bouncing RPM's?

[ALLBoostAWD]

Just installed a new EPROM ECU. 91-94 ECU into a 90. Swapped the #6 and #14 wires on the harness. Now when i drive the car, the Tachometer bounces around, but there is no misfire and there is no check engine light. I recently changed he coil pack after frying one on a hot run. Is this something that the transistor or coil pack will cause,r can it be a bad ECU??

 

[DSM90AWD]

The 1990 also uses an external tach filter that is mounted under the intake manifold wheras the 91-94 uses one internal to the Ignition Module. Did you take this out of the equation in your install?

 

[ALLBoostAWD]

I did some checking around, and i cannot find anything regarding this part. Is it called something different, anyone have a part # or something?

 

[DSM90AWD]

THIS is the guide I went by. Although JeffO has a different method posted HERE

 

[ALLBoostAWD]

Thanks man!!. Contacting Keydiver about purchasing this tach adapter.