E3.66 Premium Automotive Spark Plug with DiamondFIRE Technology - High Performance Spark Plug for Cars, Trucks & SUVs - Pack of 1 - Ideal for Engine Optimization & Fuel Efficiency

So to provide some background info I have been suffering horrible misfires on cold starts and hot restarts for a month or so. I replaced the coilpack and wires. Did not replace the plugs, because the NGK Iridiums were only two years old. On reflection, I strongly believe the NGK's are fakes as they should last more than 15k miles and 2 years. They came out looking kinda crappy.I slapped the E3's in my '06 PT Cruiser and she started cleanly. She has started mis-fire free for the last 7 starts just fine. She feels a lot peppier on pick up due to a more complete burn. ProjectFarm on YouTube has an excellent video demonstrating how these plugs are different.I took a 50 mile exuberant drive to test the plugs and ensure everything was running smooth. My gas mileage doubled from 13mpg to 26.4mpg. These plugs are the real deal. I am interested to see how they hold up long term, I will pull them in 10k and perform a thorough check on the plugs. My valve cover gasket and seals are new, and I have new injectors and coil and wires so it should be the optimum condition for the plugs to work. So far I am quite impressed.My engine has a noticeably different running sound too. I don't have the words to describe it, but it sounds more like a complete compression stroke. Maybe this is due to the proper gas burn from the diamond shaped tips. The engine sounds less rattly at idle, and my idle is much more smooth now.I actually got scared away from these after seeing some reviews and attempted to cancel the order, after being unable to cancel and trying them out I have decided to keep them in. They weren't expensive, so no big deal.