Does anyone know whether or not a brake booster off of a 90 LS will work on an 88 CRX si? I would like to replace my stock booster and my buddy has the booster off of his 90 LS I can have.

 

I didnt get a chance to try it yet, but if it does fit you will also need the master cylinder. The bolts are on a different slant as compared to the stock crx cylinder. One is like this / and the other is like this \. Just look at it, you'll see what i mean.
If i was to guess, i'd say there is pretty big chance it will fit but like i said i havnt tried it yet.

 

just change out the master cylinder with one out of an 89 Accord LX-i