I have 91 prelude si with b21a1. My transmission has 4pack shift solenoids. The only parts I find is the 2pack. Will this work or what do I need to do.

 

I don't know where you found any solenoids for sale, I can't find them anywhere.
But anyways, if you look at that valve body, the solenoids unbolt from that valve body in pairs. So maybe that's why you found twin packs.

What's the issue?

 

Here is the procedure in cleaning your current ones - https://www.preludepower.com/forums/...d.php?t=350241