@hvac Benny I completely understand that and it is the same in my line of work (performance engines).
@HVAC1000 this is also something I understand, although the majority of products do not require training on the product for someone to be a dealer, just a buy-in.
From the little I know about home hvac systems and my own trial and error work in the home, I am pretty sure that my heating and air ducting is sub-par. There are gaps in all of the return ducts, nothing along the trunk and returns are sealed to anything, including other ducting, the trunk is the same size from the furnace to both ends of the house even though they are substantially different lengths, and there are 6" ducts running to every room, whether its a 25 sq./ft. half bath or a 120 sq./ft. bedroom.
I am probably sure that there are tolerances for duct diameter just like there are tolerances for engines, and even though the work can be within the tolerance it can perform like crap.
I guess I will do what I can in order to save myself money and then start saving up to pay someone else to do the furnace. Any other comments and suggestions are welcome!