Matt,

Surely you mean that your idling with 7 degrees of advance, not 7 degrees BTDC. I have also noticed that the leaner mixtures want less timing. I don't have to worry about emissions, so I tune my engine richer with more timing and my engine seems to like that the best... at idle and cruise. On the engines I've tuned that have to pass emissions, a good compromise has been ~14.5:1 AFR and 17-19 degrees of TOTAL ignition timing... and the cars pass with flying colors.

It's interesting that moving the lambda sensor closer to the head helped the response time and thefore injector pulsewidth stability. I never could understand why some of you guys had such bad luck getting the idle pulsewidth stable, but this makes sense. How far from the turbo is your lambda sensor now? I also shoot for ~24 inches.