NGK says as a rule of thumb you should drop one heat range for each 100 horsepower over stock you are. This is pretty much BS, it seam to me that viii's run well with one step colder and ix like the factory heat range.

Also i have experienced these ignition miss fires and a common culprit is the plugs wires. i was down to .018 on the gap and it cleared it up, but when it was rainy or moist it would still do it so I knew something was up. Replaced my plug wires and ran 37psi on a .022 gap no issues.

 

My car is breaking up the same way. wouldnt let me get past 4k. Sounds like a 2 step everytime i try to push it. Started happening when i started running the meth. Should i get a different or stronger spark plug since im running meth ?

 

Gap to 0.020" ignore all the other sage advice in here, make sure the AFRs arent dead rich now that its running meth. Hopefully its been retuned for the meth injection.

Remember the correct plug for your IX is the ILFR7H...anything else isnt gonna work.

aaron

 

it never act up before but It started after I was running it constant. I changed the plugs to denso's. Are those better than the Ngk ? I also got a cam position sensor code that popped up. The afr is running fine on idol. Runs rich on WOT

 

You need one step colder plugs when you are making approx +100hp over stock power.

Using a one step colder plug on a near stock car shoudnt cause any major issues, but the plugs will most likely foul quicker. Best to stay with the stock heat range at that mod level.