Originally posted by wgknestrick
Wastegate diameter is pretty much the only variable that is directly linked to boost creep. A spring will do nothing to help creep. The boosts "creeps" because the wastegate is completely open yet still cannot flow enough exhaust through it to control the boost. Whether it "flows" enough exhaust or "is large enough" to equal the pressure differences is a moot point because this is the same thing, just worded differently.
Downpipes can also contribute (read HKS and stock designs)
Wastegate shape is also a very large factor. The IHI housings have a sharp 90 degree turn for the gas flow to the wategate hole, this is no good. It helps to round off the edge internally. The AVO turbine housing on my XS500 turbo has a rounded wastegate path already.
I will also step up and remind everybody that I was the first person on NASIOC to port a IHI turbo wategate, on a VF29, on Feb. 15th, 2003.