Yeah, oil deposits play hell with the MAF. Had a K&N filter in my '04 'Vette for 3 months, during which time it pinged horribly and overall ran like shit. That was my first and last non OEM air filter.
Might not help, either. If put in through the spark plug holes and soaked, where does all that crap that busted loose go? If not out the exhaust, then maybe between the rings and cylinder walls? Bad scene, baby! This is a concern I've read some folks have with soaking oil coked intake valves on DI motors.
I believe it does. If I understand things correctly (from my '04 'Vette), the PCM retards engine spark timing for the duration of the shift to lessen the load on the transmission internals. I also think tuning will remove/moderate that.
With the 6.2 motor, I get ~13-14 around town and ~15-17 freeway, with my all-time best being 17.4 mpg. I do the speed limit in town, but run ~75-80 highway. EPA rating is 12/city, 18/highway, 14/ combined. The truck has 10,600 miles on it, and I expect gas mileage will increase slightly as the motor finishes wearing in.
Just my opinion, but I'd leave whatever oil they put in longer than that, with an eye toward monitoring oil consumption and overall competency of the repair. That way, if things go south, they can't blow it back on you for "changing to synthetic too soon after the repair for things to fully seat".
At any given time, there are few 6.2s in Northern California...however, there is usually one here in Chico. Guess Wittmeier just knows how to order trucks right.