Okay, here's my limited info. The turbo should not change your mileage negatively. It may improve it, if you can keep your foot out of it. My CW V8 gets almost the same mileage as my cammed 4. Wagon versus sedan, bigger tires vs smaller, I'd say even when i don't put the foot down.
I would much appreciate any info on the air when you put it in. My wife would go to more shows and cruises if we had in the CW.