I'm experiencing misfire when NLS since I installed the Supechip tune, always P0303 code. I had the smae code last winter and had the coil pack replaced under warranty. If i go back to stock, the misfire is no longer there. What could it be?

 

Could be too much boost for your spark plugs. Check the gap. I have the best luck at .032" gap.

I saw this misfire when I was running the original Trifecta tune, could be rich too. Hard to tell without being able to log it. Try to NLS around 5800 rpm and see if it still happens. You might be bouncing off the limiter and not knowing it. The tach climbs slower than the rpm's, especially in 1st & 2nd.

Edit: Only pull the plugs from a cold engine. Aluminum heads you know. Torque to 15 ft/lbs.