Stiver3

Hi,
Just fitted an autoguage boost guage to my 97 Sti, installed it all properly using the T-peice, and connecting it to where my dump valve hose goes into (vacumn i think), all works fine, but now i cant hear my dump valve( only a subtle forge one) and my turbo takes longer to spin down than normal when turned off...(Rollerbearing type)

I've taken a look and all i can think is that the bore of t-peice is pinhole sized, whereas the o.e hole is alot bigger, so less air is getting through?
Thanks for any help!!