Sorry for the delay in replying. Since my last review I have modded a little and ran a 13.8 at the track at I think 97 mph.
The first and best thing to do is change to a 3.4 inch super charger pulley. Before doing this you need to change the t-stat to a 180 degree stat. Also you need to change to colder spark plugs. 2 degrees cooler should be sufficient. This keeps the engine cooler and reduces knock that robs HP. Plugs were $2 each, T-stat was $10. You might as well do plug wires while your at it.
Also, before doing this I would suggest some exhaust work. For $100 I had the down pipe increased to 3 inches. The stock is very restrictive. Also, GM put a U-bend in the exhaust to protect the sensor. This is the most restrictive thing in the exhaust and you do not need it to protect the sensor. I had the resonator, U-bend and D-pipe all fixed for $100 at a local exhaust shop. This helps reduce knock and improves HP. The rest of the exhaust including mufflers aren't that restrictive till trying to get over about 320HP.
Next I made a custom fender well intake with a K&N cone filter out of ABS tubing from Lowe's. Total cost was $60. I also ported and polished my throttle body which was free and increased throttle response and very easy. Also get a TB spacer for $10. This gets the throttle body of the super charger and reduces heat.
With all this and a new racing computer you should be able to dip into the high 13's.
Next I would suggest an air/fuel control module that allows you to control your air fuel mixture. With the intake and exhaust you are running a little lean. Calibrating this perfectly can increase up to 30HP. No you should be in the mid 13's and you haven't even touched the engine yet.
The most expensive is the new computer at $200 used. I think I did everything for under $500.
I have a friend that did all this and then put in new rockers and ported the super charger and he can smoke WS6 Trans Ams and is in the mid 12's.
I had the same problem with trying to recharge the AC... I live in NH though so it wasn't a big deal, but still annoying.