Yes, you need to remove the air filter (at least you do on the M103 engines).

Then you need to clean and lube the ball and socket connections in the throttle linkage and the linkage to the transmission.

The best way to do it if you haven't been maintaining it in the past is to carefully seperate the socket from the ball and clean any grease or dirt from them.

Then use a small screwdriver and dip it into a container of ATF fluid and put a drop on each ball before you snap them back together again.

You could also get a can of HD silicone spray and spray the ball and socket. Once you've cleaned them you can subsequently just spray the connections w/o seperating the ball and socket.

What I do is service the linkage when I do an oil change since I have to take off the air filter to get to the oil filter on my 300E.