both my boost gague and boost controller says im hitting boos just the car wont go like it kinda dies down unless its in vacume. what is wrong

 

Not knowing what you have modified, I'll guess that you have an ignition problem (coil, plugs or plug wires faulty). You could also have a fuel pressure problem. How long since you changed your fuel filter?

You could also have a clogged catalytic converter. Are you still running the stock pre-cat (tends to fall apart and clog itself and the main cat at ~50K miles)? How many miles on your car?

 

it has a new fuel filter its a brand new large street ported engine with a-spec gt500r system on it and i dont have a cat