Yep, Having a good injector spray pattern can be an overall help.

Changing the coils / boots / plug wires seems to be required maintenance at the mileage you have. Between the SL and C I think I've changed 3 coils at 124,000 ish and 164,000 respectively.

Changing the valve cover gasket is super easy once you have pulled the coils. When you put the coil cover back on, watch the small white plastic vacuum line that runs down the passenger / exhaust side of the coil well. It is super easy to get this line pinched if the clips are broken and you will get an AIR pump trouble code. This line connects the diverter valve ( between the exhaust manifolds ) and the solenoid valve ( under the front plastic engine cover )

Early M104 engines had a EGR valve that hooked to one exhaust manifold and the cylinder head , the later ( 96? for sure 97+ ) had only the AIR diverter valve and an electric AIR pump.