Newbie needing help

Hi guys
I wonder if anyone can help me with some advice about my seriesIII.
The old girl seems to run ok but sometimes when coasting up to a junction
she splutters and a phut phut noise (I feel really silly typing that) comes from the exhaust its almost as if she seems ready to backfire although this has never actually happened. Any ideas?
Also she sometimes cuts out when coming to a halt really embarrasing at roundabouts!! the engine is up to normal running temprature when this happens, would changing the coil help, I have changed plugs, points and leads.

Many thanks James

how did you do yer ign timing?? the best way on these old fookers is by ear, unless you can get it on a rolling road

Thanks Slob
I will look into that, not to sure where I might find a rolling road, the last time I recollect one was coming back from the pub!