For the turbo to be the problem with excessively lazy response, it would have to be visibly damaged, such as a ground down turbine or compressor wheel, in the wrong turbine or compressor housing, or not rotating freely. I've never seen an undamaged turbo actually cause boost response problems unless it's just oversized, there's not much else that can go wrong with them. Leaking seals won't make them spool slowly and a leaking seal could be a drain issue, I don't remember what yours looks like but some turbos are more sensitive to it than others as I saw with my wagon vs my E30 when using the same drain flange. I don't know what size your turbine is but my turbonetics is also a 60 trim T3/T04E* and I make full boost quite a bit earlier, I can't remember how much earlier in 4th gear/during a sweep of a few hundred rpm/sec. But I also have an internal wastegate and terrible boost creep. I think your wastegate is causing the problem. Not sealing well, missing its seat, lifting prematurely because of a spring issue, etc. or there's an exhaust leak before the turbo. I think the power is a little low for 12psi, but not massively. If the engine is unmodified and made around 155whp NA, 272whp (1.75x155) is reasonable for 1.82atm manifold pressure. I'd check the wastegate for flow while not in boost to see if it's leaking.
*T04E compressor 60 trim - inducer: 58mm, exducer: 76mm, F1-57 turbine 65 trim - exducer: 57mm, inducer: 64.9mm​
*T04E compressor 60 trim - inducer: 58mm, exducer: 76mm, F1-57 turbine 65 trim - exducer: 57mm, inducer: 64.9mm​
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