WhippleCharged '15 5.0 ... code & shudder
 

Looking for some insight. I am getting a "Randon Multiple Cylinder Misfire" code (PO300) when I drop the hammer on my truck. I only get it at full (or almost full) throttle. Fuel mileage dropped waaaay off... power is not optimal ... I'm thinking plugs or coils .. I contacted whipple .. they want to update tune/reflash .. I really liked my last tune from them (been getting avg of 19mpg) .. until recently when this started ... I have 71,000 miles on it now.. had both cats replaced a couple months ago... I run 93+ octane only ... Boost gauge still shows 13PSI as it has since I put the smaller pulley on it. I ordered new NGK's to replace plugs .. next may be coils .. after that... me and whipple tech support may get to know each other.... My RWHP dyno'd at 647... I know right now i'm not there...

Does Whipple have a specific plug and gap recommendation? This is pretty critical with supercharged engines. Stock Motorcraft or Denso coils should be as good as anything else.

You might need need different heat plugs. Possibly colder plugs.

Here's some good advice:

https://www.ngk.com/learning-center/...ugs-heat-range

Although, Whipple should be armed with this information, especially since you are giving them the code and what you've got.