The oil in the plug tubes can be from a failing PCV valve leaving higher pressure in the crankcase pushing oil out where ever it can. Check behind the valve cover where the 1/2 moon gasket is and see if there is an oil leak there. This is typical when you have high crankcase pressure.
While the engine is running remove the oil filler cap. if it pushes off hard you have high crankcase pressure. If it sits there and bobbles you are OK
The valve cover gasket should not leak if installed correctly and torqued to the correct specifications and in the correct sequence. Do not use silicone on these gasket as you are asking for a leak, and use OEM or equivalent gasket sets.
2002 A4 B6 1.8T
Tuned and refreshed.