Garrett G42-1450 with 1.28 hotside

I'm wondering if anyone have used this turbo. I'm having boost creep issues. This turbo is installed on 2jz 3.4L with twin 46mm gates, full 4 inch turbo back exhaust and this thing creeps beyond 30psi of boost. This creep happens even with 1.1psi wastegate springs. Originally had 14psi gate springs. Only side ports are being used to get base boost numbers. Installed different turbo (Garrett GTX4508r with 1.28 hotside) and the creep is minimal 4psi netting 18psi total. Do I need to change out to smaller turbine housing? Can this new turbine wheel and housing be that much more efficient?

Not my thing, so can't really help - but what controller(s) are you using for the waste gates, and have you checked they're opening fully?

Removed 4port MAC valve. Only using side ports on the wastegates.

If you are creeping that much with a 1psi spring and creeping with a different turbo then the issue is with your manifold design and how it directs exhaust flow to the wastegates.

On such a large housing with an efficient turbo, exhaust flow will want to take path of least resistance and by the sound of it, going through the turbo rather than your gates.

Had a similar issue with a 2J recently, changed manifold and problem sorted.

I'm only getting 4psi of creep with different turbo. This same manifold works with Precision 8285, 8385, and Garrett GTX 4508 with 1.28 hotside but with this new Garrett G42-1450 with 1.28 turbine housing I just can't prevent boost creep to minimum. My minimum boost creep would be 5psi or less.

What Mike said, assuming you've already checked the 'gates are opening fully, and they are.

What worked on the other set-ups isn't directly relevant, as Mike pointed out.

Yes, I understand the one issue is the manifold design but creeping 20+psi compared to 4-5psi is some major difference being smaller turbo. Did some researching and the new G series turbo with 1.1 turbine housing flows little more than old style 1.28 housing.