There is a step in the instruction booklet that is not very detailed and adds more time to the job. That step has to do with freeing a portion of the main engine harness to reach the new throttle body location. From my experiences of installing these the harness needs to be extended. This...
Here is a graph showing mpg with a supercharger. Average 12-13mpg. Some of the lows you see are from towing.
I was running 33" tires with upgraded front and rear bumpers and a subtank.