What does your throttle body look like? If the plate is dirty, it might not close all the way. If it is clean, make sure it seals up properly. It should be water tight!

Also, where do all of your vacuum hoses go? I saw one that was routed wrong and he was reading 9 inHg! All of my connections were made at the same vacuum port, except for the wastegate. The rest were blocked off.

Chris