The car runs fine for hour or so, then it completely starts misfiring, it's barely drivable. You come in wait a while then it runs fine, for 10 or 20 laps then starts doing it again- its hit miss, but always once it's been driver hard for a couple sessions. It usually idles ok, it's when you give it some throttle. It's a new car for us, previous owner just used if for track days. I pulled the fuel pump to maker sure the sock thing hadn't fallen off or there was something blocking - OK. I hooked up a scanner and no codes. So now I'm wondering if there's a faulty ground. Can anyone point me in the right direction, checked and cleaned the one on throttle body and down by brake cylinder, and negative battery to bottom of frame. Are there any others, and anything else I can check??