Good morning yall, I've got this 2003 g35 and let's be honest me and my buddies have been looking and guessing about this whole thing! So let me start off from the beginning. Purchased the G months ago. Random misfire.. replaced the no name Amazon plugs and coil packs with OEM plugs and coils. Helped but not completely. Swapped all camshaft position sensors and crank sensor. Same thing.. a little better but not 100%. Removed the leaking plenum spacer and installed a kinetix intake plenum. Helped but same same. Couldn't get a noid light to the injectors and seen where the harness is brittle so I got another injector harness and installed. Same. Just replaced the stock cats with aam test pipes because I seen where clogged cats would cause a similar problem. Removed and replaced. Also replacing the left downstream o2 sensor and both the right upstream and downstream because both were cross treaded in the gutted cats and thought would help with cylinders 2,4 and 6 plugs from fauling out again. Car ran beautifully for about 30 mins then back to page one. I'm at a loss for words and don't have enough crayons to even think about what to do next. Any help would be greatly appreciated. Thanks again.