8.5 mpg help

[surfsup]

At first the plugs were black, sooty, not oil, I found the egr plate clogged with crap, I cleaned all the carbon out, and now the plugs look normal. I also changed the plugs, first I had the bosh platinum, then I put the bosh copper core in. Float level was set dry when I rebuilt the carb, then I set the float level at idle with the side plug out. I replace the two stage power valve with a new single stage. The car has never back fired. The car runs great, no hesitation, no lag when accelerating, The carb kit i bought was new, but an older kit, if the power valve I put in went bad, Is there a way I can test the power valve?