Most modulating furnaces are controlled by pressure differential gas valves, sealed combustion, and a variable speed draft motor.
A modulating 80% gas furnace would probably cost more than a 2 stg 95% furnace. What would be the point? Especially with the fact that 80% may be phased out in the near future. The cost of research & development would not pay dividends to the manufacturer.
I believe York uses a stepper gas valve, so maybe they have one?
Yep, just looked it up, I think the YPLC is the model.