My 1997 C1500 with a 5.7 Vortec engine is having an intermittent misfire problem on cylinder 7. It started as a multiple cylinder misfire. I replaced the spider fuel injectors and it ran good for a week or two and then gave a Po307 code. I took it to the repair shop and they replced the plugs and plug wires, the distributor
cap and rotor, and the ignition coil unit. It ran great for about two weeks then threw the Po307 code again. I'm thinking it must be something electrical. Anyone have any thoughts on what it could be?