My tial mvs is acting crazy. Help please!

[JesterX18]

So basically I have a serious boost creep issue. So much so it blew my first motor and toasted 5grand worth internals.(it hit 24psi and crushed rod bearing #3 and main #3...) Im running a gt2871r on a stock codyace fabbed manifold with a tial 38 mm mvs. I also have a aem truboost electronic boost controller and gauge. (bypassed atm). So my line is coming of my turbo outlet to the top of my wastegate. I now have a 8 psi spring installed. If I lightly accelerate it seems to hold around 8. If I floor it I hear the wastegate rip open but my boosts still climbs and the car takes the fuck off. Since this new swap it has hit 16-20 ish briefly. I need some experienced opinions here. I went with this setup to avoid this ever happening. My only thoughts are should I have the wastgate nipple on the side instead of top? and the tru boost nipple that I threaded into my turbo outlet is small and the wastgate nipple is big, good the difference in size cause the wastegate to not open proplery. I haven't been able to find anyone else with this issue. Hope somebody has an explanation.