So the other day I took the car out at night for some go fast action with a few of my friends.

After running it hard for several minutes the car started running rough (as if it had a bad tune) and miss-firing. Also noted that the WB was showing about 10-11 AFR when it normally runs at about 15-16 at cruise with low load.

So now the car runs rough a very choppy and too rich. Every now and then I see that it smooths out a bit for a few seconds but still at a 12-13 AFR, then it goes back to running rough. I noticed at high loads and WOT seems to run good.

What could've happened? O2 sensor got burn in the highspeed run? Vac leak, headgasket?

What can I log to see whats going on, it has no trouble codes.

Thanks in advance.