Cleaning Secondary Heat Exchanger?

Rizz861

Have any of you ever cleaned a secondary heat exchanger on a York TG9S080B12MP11B? This person has a unit that isn’t making excessive CO, however the exhaust smells very sharp, pungent, and acrid, but not like rotten eggs. Inside the cabinet is the tell tale signs of a blockage ie water under the inducer and on the floor near the furnace. They use to have one of those oval shaped combo intake exhaust terminations. I don’t like those because they can recirculate exhaust gases and rain rolling off the siding can get sucked into the I ntake. I believe that is what started this process as there is rust on burners and top area where the air intake comes in. I think this caused rust on burners, that rust came off eventually and worked its way into the secondary and condensate drain. So my question is would this be possible to clean or are they SOL and need a new heat exchanger?