Wen i boost in any gear it seems to cut power at 0.4 bar. This happened wen i run low on petrol 2 weeks ago but now having a full tank of the stuff, it is happening again!

The amal valve has alreaady been taken off cause it didnt work wen i bought the car.

got a bleed valve on at the mo n set as close to standard boost as poss using a boost guage.

The car hasnt been chiped. and is runnig a standard turbo

Could this be due to fuel filter, pump or could it be somthing else.

Cheers