I have 2002 wrx, that is having some major issues right now. when i accelerate in 2nd or 3rd gear it stops accelerating after about 3g's and it sometimes makes it backfire. after the driving the car somewhere and stopping and restarting the car will it act like it's running off naturally aspirated power, the boost gauge will shake and not go over 0 psi. zero acceleration after restart but with waiting a good period of time the car will run normally again besides the 2nd and 3rd gear issue.

 

could be a loose hose, just check all your turbo and intercooler pipes are secure, other than that it could be electrical issues? what about other gears???