Ok, I have read alot on this board about switching tbi to tpi but im a littl confused. I read the long post using the v6 ecm and splicing wires and all that. ok, here is the thing, I have a 91 tbi 305 car.
Question: what do I need to do to convert this to a 87 tpi set up when I have the 305tpi unit, wire harnass from the 87 and the ecm. Is this a direct bolt in or is there things im over looking.
Your help is greatly appreciated.

 

The wiring is not a direct swap. The bulkhead at the firewall is configured differently between the 87 and the 91. Same goes for the 15-way I/P connector near the ECM. Your 87 harness also has a gray 6-way connector near the ECM. That is not used in the 91 car, but needs to be spliced.

Your 91 TBI car uses a VSS buffer where the 87 TPI does not. You'll have to be sure your VSS is sending a 2000 pulse per mile signal to the 87 ECM. Your instrument cluster will need a 4000 pulse per mile signal.

There's more to consider. The best way to understand the differences is to look at the 87 and the 91 service manuals. Be sure to use the Helm factory manuals. You can get them for $30 each until Feb 28th at http://www.helminc.com