Since I have the edelbrock kit, I am going to chime in.
If I am on the highway, I get 37-39 mpg as long as the hills are not to bad. In the city I get about 31-33 mpg. I do use 93 octane which is expensive, but worth the reliablity.
If any of you are familiar with cooper's rock outside of morgantown, it is very steep. Unless you get a good run at it at 95-100 mph, you will have to down shift to 4th to get up it. Autos will downshift, no matter what.
With my car, I have to let out the gas at 5 psi to keep from going over 85 mph. It just asks to go faster. This does take some gas, but the extra power is awesome.
I run 8 psi daily and have not had a single problem with it. The turbo spools very fast, and will give you enough power to play around with. I have had it on for about 20 grand now, just getting ready to turn over 100 grand, and no problems at all.
The car is a blast to drive and get around in, and the girls love the bov....