Slight mis-fire at partial throttle...until I disconnect air temperature sensor

I have my 1973 450SL running better than it has in 20 years but noticed that under partial throttle there would be a slight mis-fire (arbitrary popping, not pinging).  Under full throttle everything was fine.  On a hunch I disconnected the air temperature sensor and it runs like a champ.  Very strong in virtually all situations I've run it under so far.  

If memory serves disconnecting the air temperature sensor forces the car to run richer.  Could it be running too lean otherwise?  Could I just have it a bit mis-timed for it to run that lean?

Thoughts? 

Google translated for my D-Jet friends over the big blue pond:
Ich habe meinen 450SL von 1973, der besser läuft als in 20 Jahren, aber ich habe bemerkt, dass es unter Teillast zu einer leichten Fehlzündung kommt (willkürliches Knallen, kein Ping). Unter Vollgas war alles in Ordnung. Aus einer Ahnung heraus habe ich den Lufttemperatursensor abgeklemmt und er läuft wie ein Champion. Sehr stark in praktisch allen Situationen, in denen ich es bisher gefahren bin.

Wenn der Speicher dient, zwingt das Trennen des Lufttemperatursensors das Auto, fetter zu laufen. Kann es sonst zu mager laufen? Könnte ich es nur ein bisschen falsch getimt haben, damit es so mager läuft?

Gedanken?

Hi Unknown,

yes it is true that mixture will run richer by roughly 20% (depends on ECU) if you disconnect air temp sensor. I would start by checking vacuum leakages on engine, fuel pressure and injectors.

The injectors were just re-built. The fuel pressure itself is fine, but I have not run the check on the volume (yet). I believe I've got a handle on any vacuum issues (my locks even work again!), but will review this site to see if there are any trouble spots I should focus on specifically. There's not that may spots, right off the engine, to go bad, but maybe I'll isolate the climate and locks to see if that is a contributor.

The darn thing runs so well with it unplugged.....but I'm trying not to cheat.

Hello,
and we still don't know your first name

Hans-Juergen

Russell Nile. The username I chose is something I use on many sites but it certainly doesn't look nice when trying to identify me as a real person.

I wanted to re-kindle this to get any fresh opinion's.  I have checked all vacuum points and they seem intact (will cut off right at the motor just to make triple sure).  I just replaced the fuel pump and have adjusted the pressure to just about 29.5.  It still pops and runs very rough with the temperature sensor connected, runs fine with it disconnected.

I ran a test against the sensor to check resistance at different temperatures and it seemed to be at spec, or at least within reasonable tolerances.

Thoughts?