The ORNL studied the effect of intake restrictions: You have less power available (which will save gas iff you're a leadfoot, but you'd be better off just installing a heavier throttle spring), but in a modern fuel injected engine, there is no change in fuel economy because the computer is able to compensate for the intake restriction to keep the air:fuel ratio at its target.
http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf
GFB, I'm glad to hear your economy has improved. However, can you verify that your mods have any impact? This calls for A-B-A testing.