Got some results from a driving test tonight. Re-wired the MAP sensor DE device to the middle signal wire on the sensor. Filled up to the neck with diesel, and drove a 30.3 mile leg down the highway to the next filing station. Drove the same 30.3 mi leg with the HHO generator hooked to the intake.

Without HHO = 13.36 mpg, With HHO = 16.06 mpg.

A couple of notes worth mention. The DE was set on Highway mode, at the 2 o'clock position on the dial. This appeared to really lean out the motor and reduce the power alot. It was really hard to hear the motor running over the drone of the tires. WHen we hooked up the line for the HHO, it did not appear to add any power or make any changes in RPM at idle or on cruise control. Tach shows about 1650 RPM's at 55mph, with CC on, no stops and flat road. It's easier to do this at night without any traffic, too.
We both agreed that leaning the motor out this far my even drop the mileage some due to the lack of power. Reset both dials to the 9 o'clock position, where there is a small reduction in power, and will do some more testing in the next few days.