What would happen if I swapped a 93 SSEi ECU into my 92 so I could use a Jet chip? Would other car brains need to be switched?

There'* really only one way to find out. Swap it in, and see how it works. I'm not sure what differences there may be in the PCM between 92/93. Just make sure you get a PCM from a donor car with your same gear ratio for starters.

Shouldn't cost too much from a wrecker, but it'll suck if it doesn't work.

Something is different between the two. Jet told me a 93 chip will not work on a 92 ECU.