Ok I am debating on running a p30 (on the b16 obd1 motors) or p72 (obd1 gsrs) ecu on my setup ls/vtec b18b block with gsr head....what are the main differences and which one would your prefer any opinions would help...

 

If you're using the GS-R intake manifold, get the P72 to activate the throttle butterflies. Otherwise use either, and disable sensors as needed. You will (should) tune either ecu to get the most power out of the motor, and they're both pretty much the same, except for some minor differences like knock sensor, etc.