For the vast majority of the aftermarket ECU systems, the only sensors that will probably need to be added (generally speaking here, kids) is MAP and TPS.

A couple of points to that issue:

- I'd wager there are very few cars which can take advantage of an aftermarket ECU that don't have a TPS to tap into, and
- A baro sensor is legal to install now under "auxiliary gauges" (I'd install a manifold pressure gauge on my dashboard and tap into that for my ECU input).
- Hell, for that matter, if my car didn't have a TPS I'd install a "TPS gauge" on my dashboard and tap into that for my aftermarket ECU.
- FOr those cars that already have the neccesary inputs from the factory (the 2nd-gen MR2, for example, has a MAP/TPS system) it's an easy matter of programming the ECU to accept those inputs from their existing wiring harness pins.

Whatever sensor you could POSSIBLY want to put into your aftermarket ECU can be justified with the open gauges rule (O2 output gauge, MAF airflow gauge, MAP, TPS, whatever senso...uh, gauge you could possibly want). Then, I'd just find a way to tap that into the factory harness OR tap it directly into the board bypassing the factory wiring harness. The only thing keeping me from doing that now is the inability to get that intput into the aftermarket board through the unmodified ECU housing and/or via the unmodified factory wiring harness.

Your (ITAC "your") only concern here should be to fully vet it to the world and have them find a loophole that you/I/they have not yet thought of...