loss of power

[chich100]

hi all
over the weekend have been having a few problems with car miss firing
thought it might be because i had to put some murco superunleaded last week (car is rica,d)but i did let the tank run very low before filling up with optimax on sunday.This morning on run to work i had to pull on to the hard shoulder twice as the car just lost all power and if i tried to accelerate through it car started smoking. on return journey this evening not as bad but still a loss of power for a few seconds then off again.car was showing 16mpg this morning and 32mpg tonight.fault codes telling me nothing.Any ideas out there,im hoping i pickrd up some crap from the tank as i left it run so low (im rearlly thinking fuel pump or relay but im in denial!!!)
RICHARD

[chich100]

have changed fuel filter as was told that local garage has had a problem with water in fuel (thought those days had gone) was ok for a while but back as before checked again under bonnet and codes tell me turbo boost to high-maf signal absent-long term fuel to rich/lean on tickover.Do i stick with the water in fuel idea and see if it will eventually clear itself ????