The Scan Gauge works great. I played with all the different gauges (you can have four on the screen at one time), and have pretty much settled on, intake air temp., ignition timing, engine RPM, and the last one I switch between the remaining gauges...fuel system loop status, water temp., gallons per hour, engine load, mpg, MAP, throttle position or battery voltage. The trip function is also great and has such features as, maximum speed, average speed, maximum rpm, maximum coolant temperature to name a few. I am really looking forward to finishing the calibration of the fuel system and start serious tinkering. One thing to note is that the gas mileage feature (instant real time readout) becomes obviously inaccurate with the MDS active. This is probably because you program the engine size, and when MDS is active, engine displacement is 1/2 of what you programmed. In other words, gas mileage indicates less when MDS is on. Also reads the codes and lets you clear them.
Got the Scan Gauge from: http://pureenergysystems.com/store/ScanGauge/index.html
Cost $124.95, including shipping. Took 3 days from order to my doorstep, then 1/2 hour of reading/studying, and then another 20 minutes to install/program. Takes two fill-ups to calibrate the fuel related functions. I am already on the first. This unit also works on almost all post 1996 vehicles and can be moved easily from one to another.