The tech rep is there to deal with warranty issues... like the rash of evap coils that were leaking in the slabs, not at the tube sheets, and they have to authorize warranty condenser/heat pump unit replacements. The supplier and manufacturer won't authorize the replacements without the tech rep checks it out. I have yet to have a condenser or heat pump failure, but have had a dozen and a half evap coil failures. Right now I am working with the local and factory tech reps and engineers on correcting major broad spectrum RFI/EMI issues with both X13 and ECM blower motors.
On my own system, through the replacement of the control board to an updated one, the use of 2 1/2 dozen snap-on ferrite beads on all the control wires, a handfull of .005 disc capacitors on all the low voltage terminals on the board to ground , and some .01 disc capacitors between L1 and N to ground, I have reduced the noise level by 18db. The current noise level is still unacceptable at around 24db, and still far exceeds the acceptable limits set by the FCC.