Hey guys, I'm new here. I recently bought a 2000 Tahoe Limited with the 5.7L Vortec and about 150k miles on it. It had been running fine, but the SES light was been on so I went to have the codes checked. I don't remember the numbers but there were two codes being thrown: Random misfire and Insufficient coolant temp. I checked the plugs and they definately needed replacing, so I put in new plugs and plug wires and replaced the fuel filter and PCV valve. Ever since I changed the plugs and wires though it's been running badly. It starts up fine and runs good for about a minute, but then the idle starts loping every couple seconds and everything shakes. I put a timing light on it and during the lope the timing mark on the balancer is dropping back to the right(driver's side) a few degrees, then it returns and the engine sounds fine, then it lopes again... I've double checked the plug gapping as well as the plug wires and they're all in the right place and clamped on correcty. I've searched around for info and I'm thinking maybe it's the ignition coil? Thanks for reading and any help would be greatly appreciated!!!