I have a 90 crx si with a b18b1 swap that was converted back to obd0. Will the ecu from an 88 prelude 2.0 si work? Neither engine is vtec. Very important that I find out soon lol

 

You'll want to use the PR4 from a 90-91 Integra. The prelude ECU may run the car but it won't run right.

 

You will find the prelude ecu will provide fuel for a 2 litre engine with whatever size injectors the prelude engine uses. If the injectors are the same size, and thats a fair chance, then you will be running a bit rich.
And then the ignition will be set up for the b20 as well. Might be the same map as a b18, but maybe not as well.

I'd go with the ecu that matches the engine as well.