Thanks swamptooth, that got me going.

I've found another way that doesn't need an extra midi track though.

In Amplitube3 context click on whatever you want to control (Volume or wah pedal) and then "assign automation" and select one of the "Param" 1-16 slots.

  Now open the automation lane on the audio track, select Amplitube3 to control, then the "ParamX" that you assigned, then click the area in the automation lane that shows the current value, context click and select "remote control" click learn and move the expression pedal and it now works using only the original midi track. 

Just enable the write automation button to start recording, but the  assignment works even when write enable is not on.

What an awesome find! Thank you!
This is by far the easiest way to do this.
The wah pedal is one of my favorite effects and this was always a pain to set up. I just tried it with Guitar Rig 5 and it works flawlessly.

yeah i was going to go that route but i wanted to test it out first.  the best thing about the automation lane method is you no longer have to configure as a synth to use midi with gr4 or 5. no additional cpu overhead!! yay!  this is why automation lanes ROCK!

Hey kenneth - anybody ever tell you you look a lot like Ronnie James Dio??

hey! have you seen this video on the blog?? http://blog.cakewalk.com/sonar-x2-the-take-lane-super-highway-tutorial-video/