1st: when i go to start my truck it idles real low, and when i take off and step on the gas i have to keep it pressed otherwise it'll shut off on me, now this was happening to me a while back but all i did was increase the openin on the throttle( turned the little screw) and it worked fine it wasnt even accelerated. now its happening again and i dont know exactly what it is...

2nd: my a/c blows hot air in the front ports even dough i set the climate control to max a/c, and this happened from one day to another, the rear a/c and heater work fine

 

First problem sounds like a vacuum leak. Check at the back of the throttle body, behind the IAC motor. The 5.4 has an elbow there that gets a hole sucked in it . The second problem is probabaly the blend door actuator, located at the bottom of the air distibution box. Do you hear a clicking noise when you try to switch from cold to hot and back?

 

Concerning Item #1. I have a 2000 EB Exibition. I also was going through this same "keeping the engine throttled" issue. My problem is that it wouldn't keep doing it. I even took it to a mechanic that ran a diagnostic on and told me he couldn't locate the problem. He offered to do a tune-up, replace the fuel pump, and other items. I decided to just have the fuel filter replaced. that went fine for a week or soand then it started it again. This time I was at work and one of our emergency generator mechanics looked at it. He removed the cover on top of the engine and while I was keeping the engine going (idling at about 400) he took a screwdriver and with the handle rapped a few times on this part called an air idler???. This part is like on the top rear of the engine, just about under the center dash area. When he did this my RPM's jumped to normal and the engine ran fine again.This partisn't very visible when looking into the engine as it bolts to back area of the, I believe he said was the throttle body. It apparenetly senses air flow and does have a moving part in it that he said gets gummed up over time. He told me to pick up a new part which cost $42.99 + tax at AutoZone. It comes with a new gasket and two new bolts. He Unbolted the old one, unplugedthe wires attatched to it and installed the new one. He replaced it for me in about 15 minutes and my problem went away immediately. That was about a month ago and it still runs like a top. Hope this might help someone.....

 

It is called an Idle Air Control Valve. I had the same problem and had to replace mine.