Strange turbo/boost problem
 

Hi,
I'm running my FD with increased boost (14psi) when i got it i thought it was on a non sequential conversion as it never boosted before 4500 rpm. Found out this was due to the increased boost so fitted a pressure regulator and then i was getting great boost from 2000 rpm.
Now the car has developed a boost problem, some times it boost fine, from 2000 rpm through to 7500 rpm. However more often over 4500 it has a hissing (which i believe is from the charge relief valve) this will go on for a couple of gear changes then i get full boost again, but some times i will still loose boost before 4500 rpm.
It seems to me that the controls for the turbos are sticking open or closed, does this seems correct to anyone else? If so what could cause this?
I'm thinking it could be the turbo control valve or the actuator or the charge control valve? Is there anything i am missing? And how do i check if any of these are working correctly?
I am 99% sure there are no missing pipes/ one way valves as i do get full boost from time to time, and i changed the one way valves to Viton ones about 2 weeks ago.
Anyone got any advice please?
Thanks for reading my essay!

Use the troubleshooting procedures:
http://www.autosportracetech.com/RX-...leshooting.htm

Inconsistent boost could be a bad check valve or a leak in the vacuum tank (assuming the pressure regulator is working).

I've checked the pressure regulator with a bike pump and gauge and it is working fine. I'll check the vaccum tank and check valves.
Thanks for the advice bud.

Check this out........ https://www.rx7club.com/3rd-generation-specific-1993-2002-16/i-have-owl-my-engine-bay-592253/