All you did was remove the air pump and cat -- the only other emissions control here is the vacuum retard on the distributor.
Here is what I would do: 1) veryify that the vac diaghram holds vacuum -- you can just put a bit of hose on it and suck on it or you can get a MitiVac or similar pump. If it doesn't, I'd get a new one, hard to get it to run properly. Also, make sure the vac servo moves the breaker plate -- if it is stuck, it won't do anything and cause you the problems you have. I don't know what it would take to fix, but since the 116 was such a rustbucket, I don't think a used distributor would be all that hard to find.
2) Test the retard switchover valve -- I don't know where it is on the 450 SEL, I'd have to check. It's on the firewall on the 280 SE, it is connected to the manifold and to the distribtuor.
3) Verify that you have vacuum at idle to the diaphram.
If all is in order, set timing to about 5 degrees BTDC with the vac line plugged and see what happens. If this doesn't work, check the distributor for mechanical advance -- the timing should change with rpm. If not, you have a distributor problem (mechanical).
If the vac system is toast, plug the line to the manifold and use the post listed above to set the timing.
You may also want to make sure you plugged the air pump lines properly -- otherwise you will have an exhaust leak if the check valve fails!
Good luck, there is no reason it shouldn't run.
If the diaph
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!