That harness has the crank sensor on it. As well as a couple of other hard-to-reach sensor clips. Some of those are a bitch with the engine in the car.
Removing the manifold is easy, reinstalling it is easy, you'll need to rebleed the coolant system, and vacuum bleeding is the best way to deal...
It's incredibly tight back there, but there is room.
Removing the front bumper is a 30-minute thing. There's a bunch of 8mm and 10mm bolts holding it on, nothing major.
That's basically the low boost one. It's gate spring.
Ecutek also has 'Valet Mode' which I'm pretty sure is the same thing, since you can't go any lower than gate spring.