welcome,

what is the car history? has it been sitting for a long time before you bought it?

I just bought a GPS to get the correct MPH and I am turnning 4,000 rpm at 70mph. And I have sweet response puching it to 80 mph.

I suggest you do what I always do when I buy a used car and that is set a baseline. Give the car a new set of spark plugs, cap and rotor, fuel filter, air filter, and sparkplug wires if yours look old.

These cars do not have PVC valves they have crankcase gases vented to intake under valve cover via a vent nozzle. The only time gases flow from engine to air cleaner is at high speeds,

http://pauldrayton.com/uploadfiles/merc/Service/W123/w123CD1/Program/Engine/110/01-040.pdf