My gsx had an mbc in it when I bought it. I want to lower the boost from the 14psi that it's at now to 12psi until I get a new fuel pump. Which direction would I turn the allen key to lower the boost. I'm assuming that turning it to the right would tighten the valve a raise boost, so I'm thinking that I need to turn it to the left.

clockwise/right = more boost
counter clockwise/left = less boost

pretty simple, make sure you got an aftermarket boost gauge b4 you go messing with it.

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Uhm... not to confuse anyone (hopefully) but a MBC bleeds off boost between the wastegate and the turbo...

So, if you close the MBC valve, you let less boost bleed off... The wastegate sees more boost, and opens earlier. Therefore closing MBC=less boost, opening MBC=more boost.

Maybe your boost controllers are different, but my MBC (just like a water faucet) closes clockwise.

If the MBC was all the way unscrewed/open (bleeding off all the boost) your wastegate would stay shut and you would overboost to all hell.

Depends on your boost controller. If its a ball and spring type, then turning in the controller, will raise boost, turning it out, will lower boost. So clockwise= more boost, counterclockwise= less boost.

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It's a joe p. I thing its the ball and spring type. I have a pretty acurate autometer boost gauge, so I'm just going to turn it a little bit in each direction and see what happens.