After dealing with the owner, the company replace my old parts and refund the money expended.
Rosie (the owner) was very kind and she and her business partner made sure that my furnace was functional. This changed my impression about the company. Probably I am an isolated case where things does go wrong.
Unfortunately I had a very bad experience with this company. After get possession to a new home and switch the gas provider the furnace stopped working. I called Flash furnace and they show up the next day and gave me a call (I was not present) five minutes after they arrive to give me a diagnostic of my furnace and replace three parts for 550$ plus 50$ visit. Next day they replaced the parts and called me again to tell me that I need to replace one of the motor for 629$ with the risk to replace the heat exchange for another 1500$. I called another company for a second opinion and THERE WAS NO GAS!, the previous owner did not pay the invoice and the gas services was cut. How the technician came with the fancy conclusion that my furnace had broken pieces without even realized that there was no gas??? Flash Furnace promised me to send somebody to check the status and refund the money but nobody showed up and now even they are not answer thew phone.