Restriction normally will not cause foaming issues less under restricted system. Over restriction will simply slow the flow. As you learned in class, the 22 psi of restriction you built into this system should be based on a target pressure of 22 PSIG at the keg utilizing a blender at 60% CO2 / 40% N.
Using 100% CO2 on even a 11' air system can be difficult particularly with temperature fluctuations and inconsistent carbonation levels of the craft beers. I am willing to bet that there are issues with the domestics as well. If anything, the pressures are cheated high to compensate for the flucuations in temperature resulting in a clear pour until you get to the bottom of the keg. Then over carbonation sets in.
If you want to be successful dispensing most ales and lagers, use higher pressure with a blender at 60% CO2 / 40% N. End result - low pour cost with high resale.
Scott Zuhse, Instructor
Micro Matic Dispense Institute