Manual no longer needed.
I deciphered the problem.
Furnace had been operating several years with no drip leg installed on the gas supply.
The gas nozzle and orifice had become 50% restricted with a rust buildup.
Although outlet pressure read good on the manometer,the gas pressure reduced greatly at the burner causing low flame and insufficient heat.
A thorough cleaning of the nozzle and the addition of a drip leg has this furnace working like new.Go to the full post