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Cold start roughness without codes or audible misfire, HELP!

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2008 335xi, OFT STG1, DCI only (but behaves exactly the same all stock), 95k miles

Runs rough, seat shakes slightly up/down, starts very easily and under 1 crank, stutters on gear change at low throttle input until warm. When warm runs like brand new. Maintenance and diagnostic data below:

-Plugs and 1 coil replaced 4k ago
-Walnut blasted 1k ago, no change in cold start behavior
-Fuel pressure in rail remains proper overnight ~75psi (and 5000hpa lpfp/150000-120000hpa hpfp hpa during condition)
-INPA cylinder roughness shows all cylinders in the green when this occurs
-LTFT fuel trims are -3.3% B1, +5.5% B2... this is concerning, WOT fuel trims are also 8% apart... walnut blasting didn't change this a bit
-Checked injector calibration since 4 were replaced under recall with HPFP in 2011, they are coded correctly
-Disconnected battery and reset all adaptions, no change

Car was CPO until recently but I was continually told "it's fine because there's no faults" so now it's my problem.

I don't want to shotgun the repair with vanos solenoids, injectors, coils etc I want to find the problem and resolve it, thanks guys!

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