Professional Products Powerjection III Failure to Repair Hawthorne California

I bought a Powerjection III fuel injection unit from Professional Products several years ago.  It worked for several years until the ECU failed and it stopped working.  I called the company and was referred to Carl.  Carl told me that if I would send him my entire unit (about $1500 at the time of purchase) he would diagnose the problem and fix it.  I cost me about $90 to send the unit to him 3 months ago.  He told me at the time that he'd get back to me within 1 month.  I have called Carl directly 4 separate times without a response.  I then chose to call his supervisor to see if I could get a response.  The receptionist on the phone interupted my story to tell me that "Carl is a terrible technician".  She promised that she'd relay my complaint to his supervisor.  I have not had any contact from this company despite my repeated attempts.  At this point my interactions impugn the entire company.  They still have my property and I want it back.  I must assume that I was duped into sending back my unit so they could use the pieces for other projects/customers.  Please do not make the mistake of trusting anyone at this company to do the right thing.  I must also assume that this type of business practice comes directly from the owner of the company.