05 Focus ZX3 A/C only cools when accelerating

My A/C only cools when I am accelerating at high speeds. My A/C went out about 3 weeks ago, and I live in Texas and it is getting hot, hot, hot! I took it to Midas and they indicated there was a hose leak. I was reassured that the compressor was good. But they wanted me to replace the entire A/C component (hoses and accumulator) and recharge the refrigerant for a whopping $900. I can't afford that cost but they gave me some song and dance about not being able to only replace the hoses. I left. My father was also trying to diagnose and treat the issues in the meantime, he checked the fuses, changed the relay, tried to recharge it, and he tried to seal it. I would like to also mention that when he put the pressure gauge on, the low end, to disperse the sealant, the gauge read 80psi while it was running but idle. He tried to bleed it off quite a bit but it never went down. This weekend, I went to PepBoys. They replaced both hoses (high and low) and topped off the refrigerant. They also wanted me to replace the accumulator and compressor but I refused. Before I left, they let me know that it was only cooling when accelerating. They were right. I drove home, about 20minutes away and the A/C only cooled when I was accelerating at high speeds. I just want an honest, educated answer. I am resigned to the fact that it might cost me an arm and a leg, but I'm holding out hope that it won't.

The vacuum operated blend door goes into cooling mode under conditions of low vacuum as is present at high speed acceleration. There's something wrong with the AC controls. It has nothing to do with what you had worked on.