Stop in for a cup of coffee

Yep Nat. gas isn't as good as LP FYI One cubic foot (ft3) of natural gas contains 1,030 BTUs and one cubic foot of propane gas contains 2,516 BTUs, giving propane about twice the energy content of natural gas.
This explains the jet change. I wonder if an existing furnace can be rejetted for more BTU output. Hate to buy a new furnace..