DA-42 instructor reported a LH ECU (Engine Control Unit) fail message when setting takeoff power after maintenance had been performed on the engine. The instructor rejected the takeoff; taxied to parking; and contacted maintenance.

Narrative

I was conducting a scheduled maintenance flight for Aircraft X since it had the engine head replaced. On the takeoff roll I experienced a LH ECU A & B fail annunciation on my PFD (Primary Flight Display). I experienced LH engine roughness and insufficient RPMS. This difference in RPMS on the left and right engines resulted in yaw towards the LH rough-running engine. I did not reach full takeoff power set or takeoff. I promptly rejected the takeoff and contacted Tower to alert them of this. In regards to ATC; I was told to exit the runway and contact Ground. When I was clear of the active; ZZZ Ground asked me the reason for the rejected takeoff. I told them; 'LH ECU A & B fail messages'; and their response was extremely unprofessional and demeaning. I offered further clarification on the reason and then taxied back to park. I alerted Maintenance and Dispatch and squawked the plane.Suggestions: I planned to write this as a mandatory report for a rejected takeoff only. However; I would like to add that I believe Company needs to continue to strengthen our relations with ZZZ ATC. Their demeanor regarding the rejected takeoff was shocking. This is not the first time they have treated me; my students; or many other Company planes in the airspace very poorly. This has become a common occurrence which I believe needs further attention.