[KAR]

I've been searching for any help at all on my cold start issue across all the various N54-related forums and finally decided I needed to post my own question. So, just to blow through the usual level 1 and level 2 support questions... I've just completed a fairly thorough resto-mod of my '09 135i. I'll leave the pertinent details below. Despite my best efforts the engine is experiencing rough cold starts (@ 12°-20° C). Symptoms-wise, it's pretty cliche; no codes, engines feels like it's missing here and there from start until it warms up; a bit of a chassis rumble and a slight backfire-like sound when it misses. Once warmed up, the engine is rock steady at idle. Warm restarts have no issues. I'm just a hobbyist, and I'm still getting the hang of this platform along with all the tools. I would've liked to include a couple datalogs below from MHD, but sorry this forum won't allow me to share the any HTML. As far as I can tell my lpfp and hpfp are running well within spec. But if I were to guess, I'm suspicious of my bank 2 pre-ct O2 sensor. I wouldn't ever ask anyone to figure this out for me, but I wonder if I might ask for help on how to go about diagnosing this problem further? Thanks!

Just the Pertinent Details:
Original stock N54, odo ~82500, filled w/ Chevron acn 91 (I know)
MHD Stage 2+ ots tune
XHP Stage 3 v3.0
New Genuine Index 12 injectors (calibrated via INPA) x6
New Eldor coils x6
New NGK 95770/5992 (Step 1) plugs, gap 0.22 x6
New vacuum hoses and hard lines throughout
New gaskets and coolant hoses throughout
New VTT Stage 1 turbos, PCV valve, inlets + outlets
VRSF 5" intercooler
VRSF Charge pipe
Tial BOV connected via BMS BOV vacuum adapter
BMS DCI
Ct-less down pipes
New Pierburg boost solenoids
New Genuine vanos solenoids/filters
New Genuine MAF sensors
New Genuine camshaft sensors
New Genuine crank sensor
BMS OCC
Walnut blasted intake
All new fluids