Lean/ rich? Maybe both? It was lean,,,,,,took the ground electrode down the tailpipe, then got sooty as it lost the ability to burn the mixture efficiently?
I had a drag car fool me ,,,read the plugs after each run, turned out the cam was going flat, I about wore the bowl screws out before I got it figured out.
So,,,,where did those pieces go? Are there any witness marks on the turbo's exhaust inlet?
RICK
exhaust inlet= I think that's a oxymoron.