Swapping EPROMS 1st gen DSM

I have a 92 EPROM ECU in my 90 AWD, with the appropiate wires swapped. The tach isn't reading correctly which is something that normally occurs with anything other than a 90 ECU in a 90 car, or so I'm told. I bought a 90 EPROM California ECU, recently so I could get some normal tach function back. From what I was led to believe the 90 ECU's have a smaller fuel map and are a bit less agressive when it comes to timing. I have no real idea what a California spec ECU throws into the mix, but judging from what the Smog Nazi's have done to that state, it cant be good. My question is, can I swap the EPROM from my 92 ECU into the 90 ECU? The EPROM is what contains all the engine parameters, maps and limits for the engine, correct? The ECU itself serves as a "player" for the EPROM. Has anyone done this before? Both ECU's are socketed so swapping the EPROMS isn't a big deal. I just want to know if this will work. Any info would be appreciated. Thanks.

I dont think there is any difference between the regular and federal ECUs on 90s that wouldnt be covered in the EPROM. I Cant see why the fuel maps would be different, same for timing. But you can jsut add the timing back in with the CAS. I would think most of the difference is in the code written to control all the extra emissions stuff, but I could be wrong. I say go for it, but I cant say I have every tried it. 2 of my friends have 90s, but they are both on 91+ eprom ECUs. If you try it, be sure to post the results. :)

Yeah you could try it, I really dont know the answer. I am one of the lucky ones with an EPROM 90 ECU.