Last week I posted on this thread: http://talk.newagtalk.com/forums/thread-view.asp?tid=260776&posts=22#M1996743

It turns out I had two problems and both involved the 1/4 inch air lines.

Problem 1:  the air line between the governor and the purge valve on the dryer would let air flow one direction but not the other.  I figured this out by cracking the line at the dryer while air was escaping out the bottom through the purge valve and the purge valve immediately stopped loosing air. (keep in mind there was no air comming out of either side, it just released trapped pressure)  I repeated the whole process again... build pressure, governor kicks compressor out and purge valve purges, fan brakes down to 90, compressor kicks on and air starts shooting out of bottom of dryer again but this time I cracked the air line at the other end on the governor and the purge valve kept on leaking.  I went back to the dryer and cracked that end of the hose again and purge valve quit leaking again.  Ah HA!

Problem 2:  the small air line from the supply tank to the governor had air coming through and would build to the correct pressure, but was not letting the volume of air through that it should, thereby OCCASIONALLY delaying the whole process of kicking out the compressor at the right PSI  (especially at high rpms).   Put on a new hose and had 3 times the air flow and compressor kicks off right where it should.

PS  Thanks for all the suggestions and help here on NAT that let me figure this out.