Regarding 38 mm vs. 44 mm ewgs (taken from Unabomber's Manifesto):
"That is a question for your turbo vendor and tuner as sometimes their advice counters the external wastegate sizing theory. The theory is that a larger wastegate (44 mm) should be utilized on turbos using low boost vs. turbos that are running high boost which should run a smaller wastegate (38 mm). Where did this theory come from? Remember…a wastegate limits boost. If you want to run more boost, you don’t have to limit it as much. Running less boost means you have to limit it more. Think this premise through to get a good mental picture of it as this concept is terribly misunderstood."
I was wrong - boost seems to be the real variable in determining which size is correct, not necessarily turbo size. But I guess when you have a small turbo, you're more likely to want to max it out and use high boost, so you'll want a smaller ewg. With a larger turbo (unless you've really done your homework and eliminated all limiting factors), you probably won't need to run as much boost and you'll still make plenty of power, so the larger one would be better suited for that application. So I guess I was partially right after all.
Anyway, the bottom line is: talk to your tuner
