I need to list all major components in a mid efficiency cat I or cat III furnace, but I can't find them!!!?

You could look at the furnace in your home. Take off the access panel and there should be, not always, a diagram of the electrical wiring and maybe a ladder diagram of the components with abbreviation of each and a legend that tells you what the abbreviations are for. It is on the inside of the access panel. There may even be the original install instructions.

Good Luck.

Inducer motor

Flame sensor

Spark Igniter or

Hot surface Igniter (one or the other)

Roll out switches

Gas Valve

pressure safety switch

high limit switch

Ignition module

Blower motor

Burners

Blower relays

Transformer

That should get you close.

Here's a link that may help you.