UPDATE: I followed a suggestion by Paul, just to rule out one thing at a time -thanks!
I first replaced the monovalve itself....same condition - little heat on start/warm up, then gone.
I then replaced the CCU and thought I had it solved. I drove around town all weekend and to my office with nice warm heat(local driving...rural roads under 45 mph or so). During work I had to make a few 20 mile interstate trips. As soon as I reach around 60+ mph, the heat diappears again!!
I have 'burped' the coolant system so I dont think there is an air pocket. I'm thinking now some debris or blockage that is restricting my water flow at a higher speed?? Are there any other moving parts in the monovalve housing that could fail? Some one had mentioned a screen in there but I dont see anything. Iam at the point this weekend of taking apart that secondary firewall and taking every hose etc off and inspect....also the whole monovalve assembly. Anybody have any other suggestions??