As to testing the power valves, check out this tool from JEGS:
http://www.jegs.com/cgi-bin/ncommerc...61&prmenbr=361
Summit has one also but I couldn't get into their website this evening to get the URL.
This little tool, used in conjunction with an hand-held vacuum pump, will allow you to test the power valve to determine definitively whether it is good or bad.