Ok, I had boost creep after I put on a Vishnu signature series exhaust w/ cat (last week) with a VF29 (have had this for awhile w/ stock turbo back). It would creep to appx 18 when I had my boost controler set to appx 12. After reading this thread I was inspired to port my wastegate. I didn't remove the turbine housing like Austin did but I do have access to high pressure nitrogen (2000 psi) so I blew out all of the shavings. My wastegate was also offset like Austin's so I did most of the grinding the same way he did.
And the result.... no more boost creep!!!
I will have to do some more runs later or in a less populated area but I got on it in 3rd gear to redline and it *might* go up 1 psi but that is ok by me.
So the moral of the story is if you have an IHI VF turbo and you are putting on a turbo back exhaust you will need to port the wastegate at the same time.