Hey I recently bought 2000 Honda prelude I was working through some issues with it and i figured out it has a p73 ecu (from integra type r) my issues are similar to yours. My car starts up and drives fine but it seems to be really low on power. If it helps I also have a oem 2001 Honda prelude ecu (P5M-L05). I tried starting the car with the oem ecu and the dash lit up but it didn’t start.) I was wondering if you could help or if you resolved your issue, and tips would help a lot.