I Just bypassed the N75 & N249 valve today and made a quick fab boost controller to peak at 16psi... After doing everything in my power, I do not know what the problem is, but I cannot produce consistent boost..anywhere from 16psi to just flatout no boost at 0(something randomly leaks,wastegate?)....
the vacuum lines are ran like other people have shown in diagrams.
I've checked for leaks and there werent any, tried my 710N diverter valve(that I thought was leaking), tried a heavy spring big boosted BOV, still no change....So after 1 diverter valve, 1 BOV, 1 mechanical boost controller, 1 homemade boost controller, I have gotten nowhere..
Of course the N75 is out of the loop and tee-d off as a seperate unit.

My only hope/best guess is either a clogged cat is causing pre-mature wastegate opeing due to back pressure, or bad wastegate actuator,
Do these sound like logical assumptions?

 

completely dis-connect the line to your wastegate and see what happens

 

sry, Long day yesterday, I tried that also**,when I did, boost just sky rockets to 17psi at throttle first time, and then every acceleration after that, the boost leaks more and more down each time the accelerator is used, for example:
17psi 1st gear, 13psi bleed by waste gate 2nd gear, 5psi 3rd gear, 0psi constant bleed 5th gear....
The wastegat leak gets worse and worse after every throttle adjustment(not just gear change)
faulty actuator then?

 

How are your vac lines ran? Have you considered just building a boostleak tester? It would rule out a leak in the system...