would a PCM from a New gen (2000 and up) Bonnie work in the 1992-1999 Bonnies?
OR
would a 1992-1999 SSE or SSEI(if a SSEI PCM would work in a non supercharged model) increase the Performance of my 1992 Bonneville SE?

Is anything interchangable with a New Gen Bonnie and my 1992 Bonneville

SE?

You can't switch newer parts in, and unfortunately there isn't too much you can do to the engine

You could drop a Series 2 in. It would require the engine, trans, and a custom tune of your pcm. Not sure about if the trans would mount or not though.

Sorry, no, you can't change PCMs Same year only. Putting in a SSEi in place of a SE will not work either, it'* the same PCM, just that the SSEi has areas turned on.