Originally Posted by Unabomber
The general theory is that an exhaust will not cause boost creep. It is the design of the VF-39 itself that causes this. Porting the wastegate should solve boost creep issues.
Boost creep is a caused by the wastegate not allowing enough exhaust gasses to pass thru it. When you increase the flow of the exhaust by changing it, you run into the problem of the stock wastegate not being able to by-pass the extra flow. Thus you get boost creep. It's a purely mechanical/flow problem. It doesn't have anything to do with boost controllers, etc.
Porting, or increasing the size of, the wastegate will allow more exhaust to pass thru the gate. This will solve the creap problems.