my evo3 big16g creaps when i downshift sorta rough from 5th to 3rd.i have the 34mm flapper, evo o2 housing, 3 inch downpipe and catback.
some times things will creep no matter what you do
but id do it for one reason, you will get bored one day and it will be nice that its already been done when you get it swapped to a 20g. atleast i know im going to upgrade mine at a local turbo shop once i get done with all the fuel mods.