fp big t28 boosting problems

[kazzam]

I got a 2g gst with ported o2 and ex manifold, 3inch turbo back, greddy bov, turbo xs dual stage boost controler, act 2100 clutch, intake, ic piping with huge front mount, 1g tb, plus others which i forgot... oh, and a ported fp big t28. Problem is when i hit boost, it doesn't hold solid to redline, it boosts 17psi to about 5500rpm, then starts to drop and drops to 14psi by redline in any gear. i have had a regular t28 turbo before and the one i got now is definately bigger, especially on the exhaust side so i know its a true big t28. I tried un-pluging the wastegate and at redline it still is 14psi. I don't have any boost/exhaust leaks. I did try to put a heavy duty spring on the wastegate to keep it closed with more force (as my original wastegate only has a 8psi spring) and it spiked to around 22 and kept 17psi to redline... Please help me out, as i have almost no top end!! its crazy... I am concidering an external wastegate in hopes i will have better boost control. any help would be appreciated.
PS: is there some way i can route the vacume lines so that the wastegate is closed longer?

 

[nine5raptor]

You might see if a friend has a different boost controller you could borrow and test with. I don't know a whole lot about the dsbc's, so I can't really comment on that, but it wouldn't hurt to try.

Another thing, could it be your bov leaking?

 

[kazzam]

I am looking for a regular manual boost controler to try it out, see how it works.. as far as bov leaking, i have a greddy type s and i don't think it is leaking. Any other suggestions?