97 Tahoe misfire on cylinder 4
 

Need help getting cylinder 4 misfire code. Changed spider injectors, distributor cap, rotors, plugs ,wires. Tested compression was 120 lbs on 4 and 130 lbs on others. Truck is 97 Tahoe with vortec 350 with shorty headers and flow master exhaust. Being I have headers the pipe on cylinder 4 is 250 degrees and rest are almost 400 degrees. Internal valve problem????