or a check valve in the fuel line to stop the fuel from draining back.
You guys are saying "but if I have no fuel then why..." but that's not what I'm saying. I'm saying you lose a small bit of prime when it drains back overnight. Not "no fuel". Just enough trickles back to the tank overnight to make it hard to pressurize on the first start. Meaning the fuel can't pressurize properly and the internal case pressure is inadequate at starter cranking speeds. Then when it fires there is a tiny air pocket that needs to be filled before the internal cavity will pressurize fully. That affects timing, ignition delay, and quality of the burn. You get white or whitish grey smoke. A lot of it.
this same exact thing happened to me in my 99 beetle. Speaking from experience.
Your injectors could be getting worn out, or it could also be the injection pump not able to achieve full timing advance during cranking. Or it could also be severely retarded mechanical timing (what you see in VCDS basic settings) or low compression or some other sort of severe mechanical damage. But most likely just what I described or check the timing.
