I'm planning on swapping out my '92 TBI system for an '89 TPI setup. I need to know if I need to do anything with the gauges that were not standard on the '89 system but were on the '92, like the electronic speedometer and the oil pressure gauge? Do I need to scavenge the wiring out of my 92 harness and scab it into the '89 or what? Will those gauges work without all that fuss? I appreciate all the help I can get! Thanks.

 

The speedo works off a 2000 pulse signal which is provided by the computer in a '90-92 system, either by a buffer device in the TBI or right off the computer in a TPI.
Re-wire your existing harness under the hood to work with the TPI system. Its much easier than pulling out your old harness and putting in a new one. By the way, why dont you keep your car speed density instead of switching to MAF? You already have the MAP sensor and its less wiring.

 

The TPI system I bought was an '89 and I'm a little warry of the possibility of having to burn a new PROM every time I make a modification that changes the vacuum pressure. Cost is also a concern, I got a really good deal on this system and money is very much a concern, and custom burned proms are not cheap, at least not for me. I also like the flexibility the Mass Air system has to deal with modifications, like a mild cam or headers. Thanks.

 

I have news for you. A MAP will handle headers or a mild cam just fine. I ran a ZZ4 cam and headers in my previous 350 engine off a 305 5-speed TPI chip.
It wasnt until I swapped to the LT4 HOT cam that I needed a custom chip. MAF cars will not compensate for larger cams any better. That is a myth that wont die.

 

The SD system is a little more touchy to engine mods than the MAF. Headers sholuld not effect your Program. I know from experience that a MAF will accept larger changes but not by much, but any modification you do, you should get a new chip or start making your own to reip the benefits of your new mod, Programming is not hard, just takes time...

Kevin, I assume you installed larger injectors to compensate for the 305 to 350 swap...