It's actually a '91 with the 22R-E motor with 179k

What is your question?

I bought the truck and two weeks later it started shaking going down the road. When I stopped it sounded like it was pumping air(like an air compressor) out of the exhaust pipe! I had to drie about a mile home. About a week later I HAD to use the truck and after a 5 mile drive I shut it off. When I started it later I thought I'd broken the fly-wheel after the POP it made!!! BUT when it started, IT RAN GREAT!!!!!! About a week later, just like the first time, it started shaking just out of the blue! Well, I'd had it and told my girlfriend to go on and drive it. She came back after about 2 min because it kept dying on her. I drove it and it was WAY worse so I called a tow-truck and took it to a shop! I figured it was the valves! They "SAID" they adjusted all the valves, but it still makes the air-compresser noise and only runs on 3 cylinders. They said that it was on 2 when I brought it in. They also said it had 150psi on all four cyl. He told me it was probly a bad piston??? And that it'd have to be rebuilt or replaced!(the motor) My question is: What should I do, before taking the head off, to ensure that's ACTUALLY what I should do!! Could a bunch of vaccum lines on wrong cause this because it has had them all replaced and I'm having troulble finding 2 diagrams that agree on the routing!