R25 sti

the problem is that when i try to hold .5bar of boost the dump valve lets by.when i had it mapped,they had to block of the dump valve.i have tried a larger spring,also tried different vacume pipes but nothing seems to help.the dump valve is a turbo smart supersonic.
is this a problem? or am i trying to solve something thats not a problem.
i was told by pat at scoobyclinic that it had to hold .5bar for part of the mapping proses and that the letting by shouldnt happen......thanks for any help.