We have had many problems with our Lennox heat pump over the last 7 years (coolant leaks, capacitors, fan motor, compressor, etc...). We had a sales person out to give us a bid to replace it. He noticed that the return air on the furnace didn't match the specifications in the installation manual. We have a 5 ton unit and he said that there should have been two return air options (one from two sides OR one side and one from the base). He also said the the the return air from the side should have been large enough for 20 x 25 x 1 filter (It's smaller with two angled 16 x 25 x 1 filters). The furnace is a Lennox G60UHV(X) Series. Can these discrepancies cause problems with the heat pump?