I use a Scangauge II. Had it for almost 5 years and love it. It scans for codes and gives you live data for all sensors installed on the car, if there is a PID for it. Customizable for trip data and such. And it works on any OBD II car, including VWs and M-Bs. Even Hyundai ;-)
It might even be able to open or close your purge solenoid, if you can find the programming codes, as it has the ability to run custom commands. There is a lot of info on the web, but quite often, specific stuff is hard to track down.
Goes for about $150, tho.