how would a P2T (99-00 USpec SI) work with a b16a 1st gen?
is it better than a p30?

 

You're talking very different things here.
the P30 is OBD1, the P2T is OBD2b and the B16A 1st gen is OBD0.

logically the P2T should run the 1st gen B16A well, if you added the necessary sensors, but it would be a pain to do, not worth it IMO.

 

I agree completely. Trying to run an OBD2 ECU on an OBD0 motor would not turn out well at all. It'd be looking for all kinds of things that the motor doesn't have. You'd also need to get an OBD1 to OBD2 ECU adapter harness.

Stick with the correct ECU for the engine.