After servicing my supercharger, I've been getting about 17mpg. Here is a bit of a history of my fuel consumption:

When first purchased:
hwy: 36-37
city: 28ish

after 15% SC pulley:
highway: 32-34
city: 24-26

after SC service:
highway: not sure? (the new Lexus for the wife is the new weekend car)
city: 17

When I pulled the supercharger, it had absolutely no oil in it. I'm wondering if now after being lubricated, it's pulling in more air and the engine is overcompensating by running too rich. I'm getting a heck of a lot more boost now, that's for sure.

I noticed that after the SC service, the engine seems to have a low rumble sound and vibration at idle. It may have had that before, but you know how it is when you're paying too much attention.

One last note, I also changed the brake booster, but I can't imagine that affecting anything.

Any thoughts would be great!

 

Going to move you to the Stock Problems/Issues area. I would check to make sure all the hoses are hooked back up correctly. Almost sounds like the BPV is in boost all the time.