Scott - i have that valve on my camaro as well - however in addition to that one there is another valve down on the subframe under the driver seat (called the hold off valve) that has one inlet and one outlet. There is a large nut on it that gives access to "something" inside.
Here is the ebay pic
http://cgi.ebay.com/ebaymotors/67-68...item2eb597320e
let me know what you think for this valve to rebuild?