Out of control boost with external! Help please

[GSX26]

Alright, so I've been having a few problems with my boost creeping/out of control since i installed my evo3 and upgraded fuel system and fmic. I finally got everything goin good and my external gate on. but the boost is out of control. the spring is a 8.7 psi but it doesnt even stop for a second there, just shoots straight up to like 20+. i know for a fact i have everything hooked up right, but there is one thing that might be why it's like this. the person that did the welding for me has about 3/4 hole for the wastegate inlet and like 3/4" piping for the dump tube. it was free for me, but i'm thinknig maybe i better take it to a shop that will use bigger piping? could that be the problem or should i look elsewhere? thanks for any help

 

[oldman]

Give us more details about where the wastegate is mounted, which gate, which mbc, how are they all hooked up....etc. As much details as you can think of.