I've been bored lately and reading about ecus. I've discovered that there is a difference between the 88-89 pm6 and 90-91 pm6 (the ecu i'm currently using). I have an 89 crx hf with a 91 d16a6 running the stock pm8. I bought a 91 pm6. The ecu doesn't work properly and its either a bad ecu, or something is not compatible. Several websites say the 88-89 pm6 does not have an external eprom and the 90-91 does. Would this make any of the internals different and cause the ecu to have different pinouts? This is mearly out of curiosity as I'm dropping a z6 in the car eventually and its not a daily driver, I bought it for a build-up.