You should definitely perform a compression test on your engine. You should see roughly 125 psi. from a good cyl. If your problem is a burnt valve, it'll most likely be Cyl. #3 exhaust valve. Also, have the cyl. head checked for cracks (if you need to remove the head for valve repair). '88 models had LOTS of problems with cracked heads and even some '89s... can't recall any problems with '90 but just be safe and get it checked out. If compression is good, you may have an ignition skip....if this is the case, make sure you use factory ign. parts (dist. cap, rotor, wires, and plugs)....have found aftermarket parts to be junk. Hope this helps.