Has the diaphragm itself failed-meaning that it won't hold vacuum and the vac motor won't hold open on high vac (idle) condition? Did you see the old vacuum valve when it was replaced? Cormethius had to replace his but that was due to damage to the nipple from the install. His and yours are the only two I have heard of. I have had my jrsc on for 2 1/2 years with no problems.
i replaced it myself,and yes it was the diaphram it self, the rubber inside on the plunger...where do you have the vac. hose for it ran to??? i was thinking that my prob. might be because i have it running to the back of the int. man. and after vac. its getting boost and bloing it that way???
Mine is also connected to the back of the manifold. I don't think that the boost should be strong enough to actually damage the diaphragm unless it was defective. The bypass valve should be designed for going from vac to boost over and over again-mine is still working fine after 35,000 miles and I run the c*** out of it everyday.