You’re talking about the TPI like the Camaros and stuff used from 1985-92? I don’t think of these as particularly rare, somewhere between TBI that’s everywhere and OEM mechanical Ramjet that’s rare. I think there’s some niche value to TPI but nothing crazy.
They work, and they can be reliable, but TPI has haters. As with anything in this thing of ours, the technology got better and did so even during the TPI years so what we have available now/what we know now has left the TPI system behind. The early TPI systems were kind of a bastardization of engine management technologies (e.g. using an ESC style distributor on an FI setup), but they became more standardized later on. A speed density setup rather than a MAF exclusive one is almost certainly better so a later version is likely gonna be the most effective.
While TBI had the advantage of piggybacking off carburetors and CCC had to take most of the heat anyway because it slightly preceded all of them in standardizing electronic engine management for GM, the tech was still fairly new, and it seemed like they got TBI correct right out of the gate as far as starting and running go. Mixture control was kinda ding-**** on the older TPIs, hence why you have an extra cold start injector instead of making the other eight do the work for you. TPI has the reputation of being hot/cold sensitive. Theoretically, cold performance should be fine on an 89-92 version, but I don’t know why the hot performance would be bad unless there’s some kind of heat soak or fuel atomization issue that are endemic to the type.
Bottom line: I think as a swap candidate it’s worth looking into as long as you understand its blind spots and strengths/weaknesses.
