I have a 96 with a 3.8 and whenever I have the A/C on just like in any other car it has really poor acceleration though I just noticed a problem yesterday with my car. I was coming off a stop light with my A/C on max and on the highest fan speedand when I hit the gas the car acted as though it wanted to bog down and I'm guessing that it somehow wasn't getting enough fuel. I don't know exactly what was going on with it but it has done it twice already today with the A/C on so I'm guessing it's being caused by lack of fuel or poor pressure in the fuel line or something.

 

Nothing wrong with your fuel supply, it is the A/C compressor sapping power from your high-performance engine.

 

When you are at an idle your RPMs arnt enough to run your altenator to produce volt for all your electrical plus your AC on Max and high fan speed. Next time you are sitting ata light, look how much your alt/volts guage drops. Are you also running a powerful stereo? may be time for a altanator up grade.