Lots of smoke - Altitude?

[Fisherman]

Did the requisite search oin altitude and found a lot of posts but nothing on my car...
1975 240D Pneumatic Governor
I noticed this last week when I drove from home at 3500' to the coast that going over the pass (5000') the car was blowing the usual cloud of black smoke while high revving pulling the hills in third. Got to the coast and while driving around (i.e. 3/4 throttle acceleration) noticed that the black smoke was a slight gray cloud not the usual "hit the throttle and look ma, no traffic behind me" thing I am kind of getting used to.
Then when driving the other day with the wife in the 240 back at 3200', I noticed that every time she accelerated at all there would be a cloud of black out the back of the car.
I know this is an age old question but how much smoke is too much?
I have been through the manual and cannot see the correct picture of my governor hence the possible altitude adjustment screw.
There is a hex head just in front of the breather to the pneumatic governor but nothing that sounds like the altitude adjuster.

Valves are set correctly, have not checked the delivery sytsem. Been running Lubro Moly additive with every tank.

Any thoughts folks?