so I've been road-testing this setup for a couple of months now. at first I was just testing "blind", and then later added a thermocouple to measure exhaust gas temperature, so that I would have some feedback on how much I was leaning out the mixture.
boarduino, h-bridge, and rotary encoder:
the IAC valve body and stepper-motor:
I used one of my asia-engineer gauges to indicate the position of the stepper-motor:
the air tube is routed through out the driver side window, into the engine bay, and into the intake manifold:
previous to all of this, my fuel economy averaged about 9 to 10 miles to the gallon. after burning through several tanks of gas to get some data points with this mod, my new high is 14.57 mpg. not bad!