Chances are you have one or more of four common problems:

Your wastegate is not closing properly.

Your blowoff valve isn't closing properly.

You have a vacuum line leak that is causing the first problem.

You have a coupler/piping leak, or an intercooler leak.


There are other possibilities also, but those are the common ones. Disconnecting the wastegate line won't do anything with the car just sitting there running, because there isn't enough exhaust energy to make a difference either way.