PM5 or PM9???

OK i Have a STD Civic hatch with a DX engine in it...They put the engine in right before i bought it and i guess they left the stock ECU....I know both engines r DPFI but i would think the 22 hp diff. would mean different fuel curves and fuel cut off and ect. Anyways i got a pm5 ECU outta my friends junk 89 CRX DX and i took mine out...It said PM9 on it....reason i got to messing around was cus i had a miss when i hit the gas off idle...not too bad but u could tell it wasnt right...I thought it was running a lil lean. Also i was gettin pissy cus it kept cuttin off fuel at 6400 consitently. So i popped in the PM5 ECU and fuel cut off is now at 6800-6900 and the miss of idle is gone..It seems to run a lil bit stronger too...Which ECU is better and what is the difference...SHould I leave the PM5 in? Can i chip my PM9 or anything, and what all can i get done to it if so?

i had the same problem with mine when i put in a 91 crx si ecu in and my shit was fukn up so i took it out. i think u might have 2 get the ecu reprogrammed but im not to sure.