Can't boost over 10 psi.

[vg30etpower]

I have an sr swapped 240sx with gt2871r turbo. The car was tuned at 14 psi, but lately I noticed it only boosting to 10lbs. I checked the manual boost controller and it wasn't locked into a selection so I thought I might have just bumped it when fooling around under the hood, but 15 clicks later on the mbc it was only showing 11lbs of boost. The boost controller is a turbosmart boost tee. The question is I am wondering if I have a boost leak, bad boost controller, or possibly a bad boost gauge, and how to check which is bad. Thanks in advance.

[compactfean]

They make a vacuum / psi gun for this. I would hook the gun up to where your mbc gets its + pressure. Close the mbc all the way and then pump up the gun. If your pressure goes way up and your boost actuator doesn't move than your mbc is working. You can also hook the gun straight to the boost actuator and see what psi opens your wastegate. I would also invest in a boost leak detector....I made mine with scrap exhaust pipe,a valve stem and air regulator from harbor freight.the hole kit cost me like 7bucks.

[vg30etpower]

Thanks for the response, I'll check for that if I can get my hands on a psi gun, the reason why I think its the mbc or gauge is because if i turn the mbc all the way closed the car holds boost right at around 8 psi(according to gauge), which I'm pretty sure is around where the wastegate is supposed to open up, but then it takes like 20 clicks on the mbc to get that up to 11 psi(according to gauge). Should a boost controller take that many clicks to go up 3 psi? I can't hear any boost leaks, and the car doesn't have a rough idle or anything.

[compactfean]

Its been so long since I've had a mbc but I think in the instructions on turbo x mbc it says to turn 1/4 turn and re test. Before I got my avcr I just used a small valve from Lowes that's screw in style to close it for boost control. $1.50 vs $80.00? You could try that and see if you can get boost to go up. If it does than your mbc is shot.

[terry_240sx]

it's also possible that you have an exhaust leak before the turbo.
happened to me a couple weeks ago