Hey I have a SHO myself and I think you will be pleased with the SHO. Thats as long as the one you get isn't a lemon. Anyways to your problem, I think its probably that the idle has not been reset on the car lately that causes the idle to jump when ac is turned on. When the battery cable is disconnected for a sufficient amount of time the computer loses its memory of all the loads put on the engine by the car and therefore has to relearn them. Examples of loads that have to be relearned are the headlights, brakes and brake lights, power steering and a/c. Its very easy to reset the idle if that is the problem but on the other hand it could be that the a/c system is low on refrigerant and will cause the compressor to kick in and out frequently. When I first got my SHO I had a problem with the car surging with the a/c on and as soon as I got the a/c refilled the surging went away. Thats about all I can think of that could be wrong but if you want to know more about the SHO I strongly recommend visiting the shoforum, its a board just like this one and is located at
www.shoforum.com If you can't get your answer there then you probably won't find it anywhere else.