yeah my car has a dump valve fitted and it really makes a high sound compared to another guy around here with a large turbo his dosnt blow halfway as mutch as mine does at only 2500 rpm 2nd gear.

will it dump false air and thats the reason engine is over fueling?

its fitted on cold side just before throttle, so i guess it makes sence the air entering the turbo is registered at the maf and then it is dumped out of the dumpvalve and overfueling.