I had a asked a question about a pressure switch a few posts back and I wanted to add this: I noticed today when I turned off the system to reset it I could hear a sizzling sound coming from the secondary heat exchange area. Could this be part of my problem with the furnace not working properly?

Yes. I have written posts just this week stating. On a condensing furnace (90%). Slow flowing drains will cause condensation to back up in the furnace, it effects the drafting and causes pressure switch issues, in some furnaces this condensation will actually get into the preasure switch and vacuum hose.