I'd like to downgrade my Fighters Impact A to plain Fighters Impact, and my Psychic Force to Psychic Force EX, tried just burning the new revision roms for PFEX and it will boot loop to a green screen, assuming there's protection chips at play here?
Psyforce should be a straight swap, works in mame. What rom data did you use? What chip type did you use? Which chip locations did you swap?
I would expect fighters impact A de-conversion to also be a straight rom swap too, that also works in mame, though the reverse seems to perhaps take some extra effort to enable the highest data line. That shouldn't be a concern if going from A to vanilla though. You will probably have to use 8mbit roms and double the vanilla 4mbit program data though, just to be safe.
I used M27C4001s and swapped IC7 and IC2 for Psychic Force EX, haven't tried Fighters' Impact yet
I used the 2.0J version of the MAME rom, there's a chance my 4001s might be counterfeit? But they burned fine.