It could be this, not sure: the cold start injector. It pumps more gas into combustion chamber when cold outside (like maybe below 40 degrees!?) If this stays on, it will result in very poor throttle response, and if it is junk it may also be the cause for the slow starting. It was the problem we had on an old Volvo.

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro