I have a 92 LS and its bogging down alot as if though its not firing right. When I pull out the spark plug wires from 3 or 4 it doesnt make a difference, I can have both of them out and it wont make a difference, but if I pull out 1 or 2 then it turns off like it should. It seems Im running on 2 cylinders . I am getting spark from all four wires and plugs, but just to be sure I still replaced the wires, plugs and even changed out the rotor. What else can I check on this to see whats up??

 

check your compression in all of your cylinders