Turbo spooling waaaaaay high!, need boost to come down......how?????? Options

[injection]

Hello doctors, get your surgical gloves on, because i need help.....
i have asked this question before with no solutions, so i will try again, maybe someone will pick up something i missed, hopefully!!!!!
basically, my 94 celica gt, which i swapped a st205 into, was up and running last may ( 2011 ), ever since then, my boost climbs to around 19-20psi, i have hit fuel cut twice, and smacked my face into the windshield the first time ( seatbelt safety ),
anyways, in order to stop hitting fuel cut, i have to let off around 5500-5700rpms, because im right on 18psi, and dont want to keep hitting fuel cut....cant be good
so heres what ive trouble shooted so far:
hooked air compressor up to wastegate with 15psi pressure....opened perfectly, quickly and smoothly
have an XS Power DP, checked to make sure the actuator clears the DP flange....it does
there is a line that comes off the wastegate and goes behind the bottom of the intake manifold to a sensor called a VSV valve???? i think its called, anyways, hoses are hooked to that and return up front, cant remember where the line goes up front though??
thats about it, kinda outta ideas

I was thinking of purchasing a manuel boost controller, but isnt that for turning up boost, or can you turn down boost as well ( explain please )
If that doesnt work....is there some sort of a bleeder type valve i can buy, to vent some pressure, or does that screw-up vaccum

Thanx, hope one or alot of you have an answer to my problem 6GC

[injection]

Evo lution, already tried capping off wastgate to tvsv, still building same #s in boost applications ( 19 - 20psi ). Put it back to stock set-up after a couple weeks of driving, nothing changed....same, this was back in August, thanx anyway....
From what i can see on my exhaust, there is a reducer on the end of the DP, its a section about 4inch long before the 3" exhaust, but the reducer piece is still quite big, 2.3/4inch,
When you say machine the holes in the wastegate, are you talking about the ports where the flapper opens up, if so, is there an easier route then that???

[evo_lucian]

Evo lution, already tried capping off wastgate to tvsv, still building same #s in boost applications ( 19 - 20psi ). Put it back to stock set-up after a couple weeks of driving, nothing changed....same, this was back in August, thanx anyway....

Capping of the wastegate to tvsv port would allow you to run wastegate spring pressure (8-9 psi) if you were going past that then I believe your wastegate flap wasn't opening all the way with the downpipe on.