Hi ponder if anybody can help, the car starts to boost up then drops

symptoms are like the the inlet boost hose is Compressing ie hose lost its
strength

i got the car warmed up today "STATIC" and when the revs hit about 3000

the dump valve starts blowing air out via up and down on the revs

is the dump valve fucked.as i carnt find any air leaks..apart from the dump leaking air out the side exits

how can i test for the problem