Midnight85

Hi guys, I am a noob here, kept hearing about how you guys are pretty good with aftermarket dfi so since I have a problem, here I am.
I have installed an Accel Gen 6 dfi on my '87 El Camino daily driver and it starts, performs, and generally runs great. However I have one problem I cannot figure out. If I start the engine cold it has no issues but once it has been driven 5-10 minutes and is sitting idling I can't turn on the ac or put it in gear without it dying. If it is cold or just warming up there is no problem at all. I am running a 350 vortec with a very mild cam and a stand alone HEI. I have changed the IAC, TPS, and both temp sensors, played with timing and throttle blade settings all the while keeping the tps set properly. Whatever this is is heat related I'm sure. Anybody experience this or can anyone give me something else to try. I should mention I bought this dfi used and did not get any of the tuning equipment such as software, cables etc.