The other day i seem to have burnt a valve. #3 cylinder has 5 psi and all the rest have about 140 psi. Very ruff running and idling. The boost gauge is also wandering from about -3 to -8 as it idles. Two days before this happened i put a new cat on the car and the o2 sensor looked very light in color ( lean ). The scanner also confirmed that. My question is what can cause the lean condition, i plan on fixing the valves but i dont want to burn up another valve. Any help would be appreciated.....

Burnt valves generally come from them not seating properly. This is how they cool. Check the valve springs, they may be worn.

Im putting all new springs on, i guess you could say a complete valve job. Im just worried about the lean condition...

You would need to scan to get an idea of what your running. Have you pulled the spark plugs and looked at them? If so, take a picture of the end and post it up.

Ill do that but it may take me some time, the cars at work in the parkinglot. The guy that sold me the car never changed the plugs and the guy he got it from probably never changed them.

Sounds like a full round of tune-up to me. Plugs, wires, oil change, air filter etc.