So the F23 is in, the IHI came out relatively easy, the install was surprisingly time consuming. Every bolt seemed to fight me for 30 mins then just magically thread right on.
All in all I would say if you're nervous about doing this it isn't overly difficult, I didn't have to fight any of the stripped allen heads or anything seized, and I found that removing the down pipe before the heat shield made the 3 bolts much more accessible.
Once I had everything installed I decided to go ahead and start it up naturally. Here I found that my battery was nearly dead (its been in the garage untouched for about 4-6 weeks... SO I threw on the jump pack and was able to fire it right up with a ton of DTCs about weak voltage. After clearing all of those I let the car idle for a bit found no leaks but did notice a ticking that sounded like a relay clicking but I was opening up modules in VCDS and decided that was to blame as it stopped after I closed everything out.
With the car not leaking anything and 90% buttoned up (including loading the F23 file) I took it out for a very short very easy drive, I gave enough throttle to have boost onset once and I can say that this thing is a completely different beast than it was at stage 2, and I barely got into it hit ~10 psi boost.
So I came home and of course the off gassing of all the oil and stuff on the new turbo made it stink and scares me that something is horribly wrong and will continue to do so till I prove otherwise, but no CEL or anything. I let it idle for a bit and still no leaks to be found, but that relay ticking came back... I'm not sure what it is but I've had it happen before when I did my brakes and was running some VCDS procedure not sure any more what the process was though.
The 2 other issues I've run into during the install and I'm not happy with are I dropped a coil pack popping it out of the motor and the clip for the coil pack on the driver's side (cylinder 4 I think... I can never remember which side to start counting from...) will not lock on to the CP, it does seat fully but it can be pulled off without releasing the clip. I tried moving CPs around to see if that had anything to do with it and no luck...
Car ran fine, but I'm going to be babying it for a few days taking short drives and checking for leaks and gradually increasing the throttle and distance.
Then I'll do the final button up with all the inner fender, belly pan, engine cover, etc.