If you ever have the time/funds, the electronic ignition can be a great job on these engines. Much less susceptible to damp, as well as smooth running. If your carb is mis-behaving and difficult to set up, it could be worn. I believe the spindle and throttle plate can wear, making it almost impossible to get consistent idle settings.

Weber CARBURETOR SET UP AND LEAN BEST IDLE ADJUSTMENT

Wind the idle SPEED screw out until it is just touching the stop. stamp on the pedal a couple of times then wind back in 1 1/2 turns.

The thing people rarely tell you: There is no point in trying to set up a carb properly unless it is UP TO FULL TEMPERATURE. Get it running as best you can then take it for a HARD drive to get the engine HOT. Then run through the carb setup again. If you don't set it up warm then you will set it up rich as the engine will need choke which you will build into your tune.

Don't just let the engine idle to warm it up - Landies are overcooled by the permanent fan and will never get up to a good temperature.

You should be able to get a decent mileage with the weber ~16-17mpg on easy runs if you set it up well in a 88"

D