I have a 2 year old Dukane 70,000BTU 92% gas furnace at home, it is slightly oversized, 63Deg Temp rise with 3.5" Hg gas pressure to manifold which is OK, it works great but my question is how can I de-rate this furnace a little to keep it running longer. My thought was maybe drop to say 3" HG gas pressure to manifold or lower but would that alone cause any other problems? I've been in the business long enough (but not residential) to accept if its working properly Leave it be!