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It seems to take a LONG TIME to spool up and make its power, more like a BT
What was up with the original actuator?

I'd just stick the OEM one back on then. I bet you find your power
People have done it before & it didn't work...
Can't remember who or when, but on a regular turbo the 'right' actuator is the OE one
Refit the 3 inch tip first as this will flow better boost at red line. Don't over tighten the actuator as spiking will be a problem, 5-6psi will be adequate.