W123 help needed!

[Kennygrant]

Hi I'm looking for some help/advice/ideas on a problem with my latest project - an '84 W123 280E with mechanical type injection.
The car had been in storage since last year and had been running perfectly up untill then.
The car broke down on the way back from the storage place after about 3 miles, the engine just cut out after pulling away from a junction. I could restart the engine but it was misfiring and would just cut out if I tried to drive after only a few yards.
I replaced the HT leads and spark plugs as they looked a bit old, the rotor and dist cap look like they are in good condition.
I also replaced the fuel filter and put some fresh fuel in the tank with a splash of injector cleaner.
Running seemed to improve slightly and the misfire has pretty much cleared up but the engine is not wanting to rev without coughing and sometimes doesn't rev up at all.
The problem does seem to clear once the engine has fully warmed up.
Has anyone came across a similar problem?
Any advice at all would be great.
Cheers
Kenny