Looking at the numbers, it appears your actuator could be too long. A 100mb of boost over requested is not a problem. When you get to 300mb above requested, the ECU cuts fuel to save the turbo, also if the error ( under 300mb) lasts for three seconds the ECU once again cuts fueling. Messing with the stop screw can blow a turbo, as sometimes the arm "sticks" telling the turbo to spin as fast as it can, and BOOM!. A longer stop screw is not a bad thing, at least it will prevent the turbo from having a runaway not related to oil in the intake tubing. I personally would not mess with the stop screw with the turbo still attached. If off the car go through the "standard" actuator setup it lifts off of the stop between 3-5" of vacuum, and it hits the stop at 18 or 19". If at 18" and the turbo is not on the stop screw, adjust the stop screw so it lands solid at 18". For example: the actuator doesn't hit the stop until 21", a couple of things could happen: one might be a lazy spool, and the other would be the tune is not applying enough vacuum to get to full spool. These last two things are not written in stone and may not apply to you, but there have been people these things have happened to in the past.
I have done a little fiddling with the actuator arm length, but I haven't noticed any significant difference. The actuator movement checked out using a vacuum gauge when I installed the injectors. I find it odd that the engine is getting more boost that requested, because most of the time boost is quite low (10-15psi) even when accelerating normally.
I expect the engine to put out smoke and run high EGT's at or near WOT, but the issue is that I never use WOT during normal driving, and I don't get much more than 15psi unless I really step on it. Smoke is pretty much constant, even at idle it puts out a haze that wasn't there before. I realize I do have a somewhat restrictive exhaust downpipe and hope to build a new one in about a month, but I don't think it is causing most of my problems.
Having given this some more consideration, here are my thoughts: before the injectors and Stage 4 tune, the turbo boosted fine to 18-20psi even at partial throttle, there was little to no smoke, and the engine ran very cool. The only things that have changed since then are injectors, tune, and MAP sensor, so one or more of those things are awry.
The injector nozzles are from a company in the UK called DSI, they had 150P1019 written on them and are nominally a 0.220 nozzle, but no other branding, so I'm not sure who made them. They were mounted and set to 220 bar but not flow tested. If the nozzles were poor quality could they be putting out much more fuel than the ECU expects?
I know the turbo is capable of putting out plenty of boost even at low rpm's; after each shift the boost hits 23psi very quickly and then drops back to 10-15. I can hear the vanes opening up and dumping the exhaust when this happens, which leads me to believe that either the tune isn't telling the N75 to give enough vacuum to the turbo or the vanes aren't where the ECU thinks they are. When I clocked the turbo I had to build a new actuator bracket, so the angle the actuator sits at may not be quite the same as on a factory turbo, but it is close.
The MAP is brand new from IDParts and doesn't throw any codes so I don't think that has anything to do with it.
Sorry for the long rambling post, hopefully its not too muddled to make sense of!
