Since I posted in here I figured I should give in update on my situation. Might be helpful for you as well, but then it seems like you may have already checked the exhaust valve. So I found the source of my low boost issue 5lbs mostly, sometimes 10lbs at best. I found no soot on my up-pipes. I torn all my couplers off, cleaned them up, and inspected with no damage found. A boost leak test up to 20 lbs produced no noticeable leaks. The wastegate spring seems weak to me as I can operate it by hand, so that likely needs replacement. However, I found the arm to the exhaust brake had popped out from the pedestal and the valve had become wedged almost shut. I move it open and laid it so it wouldn't flop back close and found I was now making 22psi (TS - 100hp tune on an E99).

 

Nice ya I'm about positive it's my up pipes I have two places it's leaking from one small one quite large! Sucks tho that's gunna be $500 bucks oh well it'll help with performance some!!!