There are alot of things it could be. Pegged boost gauge and poor accelleration could be an indicator of a clogged catalytic converter, especially if the car has been sitting. Crawl under there and punch it. Do you hear anything? If you hear rattling or the sound of sand shifting around, change it. The cat can also explain some of your high temps
Also change your plugs, wires, air filter, pcv valve, have your coolant and trans flushed, and remove and clean the throttle body. You are in need of a major tuneup.