To4e 40trim with a .70ar hotside and a .50ar cold.
Straight T04e or t3/t04e? eBay or some actual legit brand?
Either way, if you believe in compressor maps, you should be able to make 350-375whp with a 40 trim t04e compressor wheel. If you want to find out if it is compressor limited, crank the boost to 30psi. If the boost falls to 20-22psi by redline, you're compressor limited.
I can't see it being turbine limited based on how laggy it is. I have to assume the turbine wheel is larger than at Stage I T3 wheel, so already I know that the turbine wheel is probably not the issue. On top of that, .70 is a pretty big turbine housing.
My guess is, with 2-3 more psi, you'd see 320-330whp and that's it. It's probably held back by the .50ar cold side enough where it can't hit 350-375whp. All in all, it's just a T4 turbo on a 1.8L engine. The results should be expected to some degree.