Was hoping to get some suggestions for where to start my diagnosis...The car is a 1980 245DL B21F/M46. It runs smoothly with as much power as it's ever had, but gas mileage is around 2 MPG worse than it used to be and there's always a weird almost sulfuric exhaust odor when I get out of the car - not an unburned fuel odor. Spark plugs and wires are new, cap and rotor are new, O2 sensor is new, air filter is new, converter was replaced a few years ago, valve adjustment just done (no change). On my list are O2 relay, ignition timing...anything else? What should be checked first?

Thanks

Zack
1980 245DL M46 273k
1988 745T+ M46 195k