cheerz again.my vr is losing power,seems like its spluttering a bit with some backfire at times,theres just something not right

its gotta be 1 of the 2 tho as i have changed pretty much everything else that it couldve been,it sounded like a maf problem to start but i have now changed that for a new 1 but still its not right?! its had new plugs n leads,new air filter,new fuel filter,fuel pump replaced,new lambda sensor all within the last 2 months while trying to source the problem,had auto eleccy out he said lambda,did that no joy,got towed by AA he said maf,changed that and again no joy! it was working fine for about a week then it just didnt want to work 1 morning,and thats been it for a few days! any help would be appreciated as im stuck!
