What's the story on the throwout bearing?

I just recently fired up my BPE 427 LS3 and the tune is good enough to fire up, but it's very far from being good enough to count on as-is. The first ECU had a corrupt VIN and wouldn't let me flash a tune. They sent another ECU and I was able to get in. The STFTs were immediately adding fuel due to a lean idle condition. I've since turned off all fuel trims and started MAF tuning at idle. I'll be driving it over the next few weeks to dial in the MAF before going after the VE table.