Not sure if I should bump up an old thread, so decided to start one instead. My tuner says that there's something wrong with either my MBC or I have a boost leak. I performed a boost leak up to 10PSI and leaked at the throttle body and my VIII DV. So I had both of them replaced, but now I don't have an access to an air compressor.

My 3rd gear data logs reveal that I hit 24-25PSI at 4000RPM, isn't that a little too late? I read that the VIII turbo reaches full boost around 3200RPM. My tuner says there might be a boost leak and something might be wrong with the MBC.

My mods are: Buschur Intake, IX DV, Ported 65mm Throttle Body, Walboro 255 fuel pump, Trust MBC, 3 inch Downpipe, Cat Delete, and 3 inch exhaust.

What could be the problem? I'm going to check the wastegate actuator to check if it's loose.

 

Replaceing your wastegate, and inspecting your flapper would be step one.

 

See this is the thread I needed to see. My car is hitting peak boost of around 24psi again at like 4000rpm, when it should be hitting at least 500rpm sooner. I am debating running another oem wastegate actuator or an aftermarket one?

 

And since you are running an upgraded downpipe/exhaust, it should spool even sooner.

 

Check the preload in the wastegate, and that it functions correctly.

You need to boost leak test to the psi you are running, or a psi higher. 10spi is not enough, you may still have a leak.

The 65mm ported throttle body will slow spool slightly, but will help on the top end.

Also, just for clarification, peak boost wont hit at 3200. That is where you hit your peak load. On mine peak load of 280 is 22psi @ 3250, then I hit peak boost of 25psi @ 3500 and load of 270.