Audi A6 Repair Question
Check the coolant temperature sensor, this one is used for cold fuel enrichment prior to the oxygen sensor taking over the fuel adjustment when it goes in the closed loop.
Sparkplugs is not a complete tune-up-others such as cap/rotor/fuel filter/air filter etc.
Also may want to check the throttle position sensor this one informs the computer where the throttle at all times.
Try running a scan tool to view the fuel trimming and other serial data stream.
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