Getting code P0442 on 2006 Chevrolet Trailblazer

Can't seam to correct the problem with getting code P0442. I changed gas cap, purge valve solenoid,vent valve solenoid,and had smoke test done,know leaks detected, seal for filler good. Check engine lite still comes on, with same code. Don't know what to try now.

It is possible the fuel sending unit has developed a small leak at the top of the fuel tank itself. Gm extended the warranty to owners in the northern states to 10 years for this problem. Call dealer and see if covered and have checked.