Have you noticed any loss of coolant. When my turbo bushings went out on my 1.8t, white smoke came out the back. White smoke (steam) comes from coolant leak into either exhaust or combustion chamber.

 

blue smoke means ur burning oil... your piston rings could be worn out or something could be leaking oil into the intake manifold...

 

So I finally fixed it. I had a bad headgasket. It failed and I had combustion gases coming out of my coolant reservoir which i checked with a basic block test. No more smoking and smoother running but I am still getting horrible mileage. Last full tank only went 220 miles. I have tried all the things mentioned. Any other input