My friend just purchased an FD this week and is having some boost issues. I've looked over THIS link and his boost problem is pretty similar to THIS problem.

His car has a catback and a turbo xs boost controller. You can adjust the primary boost from 4psi all the way up to 10. It hits the adjusted boost for maybe half a second(spike) and then it drops to 3-4psi all the way to redline. I didn't have enough time to trace every vacuum line but all the intercooler hoses are on tight and they are fresh without cracks. He has his BC setup in version two so that there is pressure source to the BC then it splits of to the wastegate and actuator. I'm gonna work on it later today so i wanted to get some ideas from the "experienced" crowd.

 

There is not much to say but to start working through the troubleshooting guide you have already linked in your message.

Now, the boost controller, no matter how good, cannot adjust the boost below the wastegate spring level. That level is about 7 PSI. So if you are getting below that, it points to a problem with the turbo system. Unfortunately, you just need to start checking things one at a time. Concentrate on getting the primary boost working perfectly first, and then work on the secondary boost.

Use the overview to see how the components are behaving through the rpm range on a boost run (i.e. WOT):

http://www.autosportracetech.com/RX-...erOverview.htm

 

UPDATE:
So I wired the car in TTC( wired the compressor side actuator and the turbo control actuator open) Just to see if we could get some boost but no cigar. We kinda heard a screech noise at wot in the upper RPM. The boost controller is set to as high as it will go which is like pulling the hose off the wastegate. After looking at some of the pipes under the engine bay i notice this crack on the y pipe and it goes all the way underneath. Could this lose 5+ lbs of boost, because the car won't boost past 4psi.

 

My boost controller can't go below 10 psi