Hi Sean,
When your tank is located lower than your burner, your are very prone to airlocks (and oil areation)
So, a tigerloop fitted to the system will address some of the problems with getting the oil up to your burner as it's function is to remove the air from the oil (it bleeds out through the top of the dome) it must be installed outside, not beside your burner. You pump should be good for at least 1.5m draw up from your tank, did your burner always lockout when you had still alot of oil in the tank? and was ok once refilled?
Then from the tigerloop, there is 2 flexible hoses that run to the bottom of your pump (when he is fitting them, remind him to fit the 'grub screw' to the return side on the pump, of you will loose a pump!)
As regards the smoking, it could be this over areation of the oil, or oil starvation, but your technician should also consider the nozzel (i assume he replaced on the service) may be duff, and he should try another one.
Let me know how you get on, ok.
T, March 2008