Check and make sure you have any ports you're not using on the wastegate blocked off. This happened to me, one of the ports that can be used for a nipple, I had forgotten to tighten and locktite the plug. Post-Tune, the plug managed to come out and I was overboosting non-stop. Come to find out it was just that

 

You only use one of the lower ports and plug the other two. One of my plugs had come out.

 

Did you plug your water port as well? All mine are plug except for my water port.

 

No, you don't need to plug the water ports.

 

Are you running a mac boost solenoid? If you are can i see how your vacuum lines are hooked up and how is your solenoid wire?

 

My s2000 isn't turbocharged, my old car was and I had this problem.

But, to answer the question about the MAC solenoid plumbing:

 

Update 12-22-15

I did another boost leak test and found out that my compressor wheel boost source has a leak and I have two leaking coupler.

I plan on using some hair spray to seal the coupler.

The boost source on the compressor wheel that supply the wastegate and solenoid with pressure is another story. Garrett turbo didn't have a boost source tapped on so I ended up doing it myself. Everything looks good until I realized yesterday that when I tapped the housing. Instead of tapping straight down on the highest point. I tapped it off a little to the side. When my taper push lock is screw in. Once the higher point seals up, my lower part is still a little open and causing a boost leak. Hopefully this will help with my overboost problem. I'll keep everyone posted.

 

Hey did you ever find the cause to your boost creep?

 

I fixed some leak and redid my down pipe/exhaust the car still is overboosting. Time to just go to a tuner now.

 

Bump