Hi I had a similar problem. Try this, tap the centre of the fuel distributor with the handle of a screw driver quite hard. Then disconect the electrohydraulic switch at the back of the distributor.
This worked for me as when the fuel cuts off on the over run it didn't come back on again. I tried another one and the car runs fine
Also when I was readjusting the air disc hight I once ended up with a mixture so weak the car would't start I solved this by turning the mixture screw, see your manual
Neil Farrow Exning Suffolf UK