Oxygen sensor and fuel throttle pos. sensor codes plus......

I have a 93 Surburban and it was slow to begin with, but about a month or so I got a check engine light. As soon as the code came on, well the next morning, it has started to die on me every morning. I took it to auto zone to read the codes and it read oxygen and throttle positioning sensor codes. What happens is this......In the morning when I first start it, it starts, but as soon as I put it in drive or reverse, if I do not give it gas, it will die! After starting it again and try to move the truck sounds and feels like it backfires and slowly moves. The burb has no power! Even on the freeway, when I try to pass someone, I punch it, and it slowly picks up speed. I have replaced transfer case, transmission, starter, tension pulley, and many other small stuff. So, I don't have money to keep buying parts so I need help to get as close to the problem as possible. Some friends say it's my fuel filter others say it's my spark plug wires and spark plugs. Help.