Hey y'all,
So i have a 2003 350z Auto that i bought in December and its been such a great car, it got me through the winter and even the Polar Vortex we had back in January here in the Midwest (LOL). So anyways, the misfire started in April when the weather started getting warmer here. I was driving somewhere doing errands and i noticed that the car would start doing a loud humming noise and i saw the RPM very very slowly start dropping until it got to around 1k RPM and it would drop down to 750 and bounce back up to 1k then come back down normally when i came to a stop. Then i saw whenever i let go of the accelerator the needle would immediately plummet down to 1k RPM then bounce up to 1.2k RPM and then come back down normally. So i suspected it was the Spark Plugs. As i was changing them, i noticed that there was oil inside of the spark plug wells. Inside of 1 and 2 was little oil while 3 and 4 had none and 5 and 6 had a lot of oil. I cleaned it all out and then i changed the spark plugs and gapped them to .43. It didn't get rid of the misfire so i changed all 6 Ignition Coils and it didnt work either. Then i moved onto the Throttle Body and MAF sensor and cleaned both as much as i could using their perspective cleaners.

So now i am at the point of where im panicking because there is NO CEL and what's worse is that i had it diagnosed by 2 mechanics (Including the Dealership!!!!) and they told me everything was running fine. Hell no it's not. I've been looking all over the internet for anything related to RPM plummets and nothing comes up! I'm at the point where i'm just going to drive it and wait for a piston ring to blow up because i can't find anything wrong. I also changed all the Vacuum hoses except the Upper Plenum hose, Brake Booster hose and the PVC Valve.

So i turn to you guys for help because i just feel the car getting weaker and weaker as i drive it everyday. I also have a video with proof i'm not crazy.