We're talking about different things with on/off vs linear transition of power. You're talking about power delivery at full throttle, through the rpm range. Yes, in that situation, my turbo kicks in pretty quickly in the 2500-3500 rpm range. Not like an on/off switch, but a very quick ramp up in acceleration.

I'm talking about part-throttle throttle control under higher load at more stable engine speeds. If I'm at freeway speeds around 3000 rpm with my turbo, there's a very smooth relationship between pedal position and boost/acceleration. With the 3.8 Sprintex kit, I could feel a small harsh transition when the bypass valve opened/closed as I smoothly pressed/released the pedal through a certain position.

Yeah, I looked at that PDF. It was pretty cool, but I don't think it's really relevant to the decision of adding an aftermarket bolt-on FI kit onto an existing NA engine. That document was about using FI with a smaller engine to get similar power with better fuel economy compared to a larger NA engine. We're talking about adding FI to gain not-entirely-necessary additional power on an already completely engineered stand-alone OEM NA engine.

More importantly, that document is about a small engine with FI developed together as a complete OEM package fully integrated with the ECM. In OEM packages, the ECM has control over the bypass valve (for superchargers) or wastegate (for turbos) to have much better control over when boost comes in to play and how much of it. A bolt-on kit will never be as refined as an OEM system, because the ECM for an NA engine does not have the programming in it to electronically control a bypass valve or wastegate in relation to everything else going on with the engine. Bolt-on kits must rely on simple actuators controlled by manifold pressure, calibrated by choosing which strength spring to use in the actuator. This gives much less control and requires more compromises to ensure that significant boost does not come it at times that would be incompatible with the operation of the ECM programming that doesn't have the flexibility to be fully aware of boost transitions in its calculations. For example: closed-loop mode.