This is another issue I have.
I have a gt2554, ported the wastegate opening and also ported the downpipe. This helped a lot with the boost creep. I couldnt get it to run under 12psi over 5500rpms.

But the issue here is,
1- Sunday, it boosted only to 8-9 psi (this is my goal) I never hit the boost limiter. The temperature was 60 degrees.
2- Today was 10 degrees, it overboosts to 12 psi in any gear over 5300rpms. My duty table is already set up down to 10 at 4500rpms and 5 at 6000 rpms. Those are really low numbers and I just dont want to change my settings every time its cold...It makes driving this car a pain in the ***...im really getting tired of it.

Does what I say make sense? Is there a cure for this boost creep? It happens every time its under 40-45 degrees outside, I guess theres more oxygen in the air.

 

off the cuff, I'd say that cold air is denser, but it's being heated up and expanded by the turbo, making an overall increase in the amount of air that needs to be dumped at higher revs. so while things are able to maintain lower psi at higher intake temps, you're running into the barriers at cooler intake temps.

that doesn't explain how to fix it, or even what specifically is wrong, just a plausible explanation (in my mind) for the cause. I could be completely wrong.

 

seems strange to me, I get a bit higher boost in the cold and attribute it to a bit more exhaust flow. My setup is a gt2554r and a 3" exhaust and i run like 50 - 60% duty cycles.

 

Yeah I wouldn't really say the EBC isn't working. You have 5% DC at redline...that's pretty much wastegate pressure, you can't lower boost less than what the wastegate will boost. So the EBC is working, you're just making more boost in cold weather than you want.