I am going to stay away from this. I do not believe for a minute that a 97.5 furnace will run at 50%. I do not believe a combustion test can show proper readings on modulating furnaces if thats the case.
The new York. Luxaire vary the blower motor on all models, not just using 2 or 3 speeds either. Also the induced draft motor varies as well.
Do not believe this thread.................!