I've searched around and think I may have a valve problem. The number 2 and 4 cylinders are not firing, we've changed and tested the spark plus, fuel injectors, PTU and coil packs. Also did a compression test numbers are good. Also verified that the wiring harness is good. The car is a 91 NA stock with 125,000 miles the heads have never had any work done and the car is only driven about a thousand miles a year now. Any one else run into this problem?