So are you just venting to atmosphere now? Is it 100% blue smoke? If it is then you have oil getting into the chambers somehow! If it's black smoke then your just overfuelling, and if it's white smoke (steam) then it's water so could be head gasket.

As the return to the metering unit is blocked off and if it is blue smoke the only way oil is getting into the fuel/air mix and being burnt is past the piston rings or your valve stem seals have completely disintergrated!
As i said above get a compression tester and do a compression test, they are only about £15 from halfords!
If your Comp is good (150psi min across all 4) then i'd go with stem seals, again only if it is 100% blue smoke!