Hi Cliff - Playing with making my own stuff now on this factory, I am making Steering Wheels and Heated. I noticed on the componant usage, that I am making 78 an hour, and using none. I think it may be just an error that its not picking it up correctly.
Here are the slots cranking out the basic steering wheels. Looks like the need A Basic and a Heated when those are installed.
Interesting. I’ll look into it
edit: Are ALL the cars in your range using only heated steering wheels (with no base steering wheel models at all).
It might be that you simply have not fitted a base model for over an hour, yet the stockpile has kept hold of some it will use when the next budget car gets to that slot.
Well yes, as a matter of fact, They all do have Heated. I Just watched it more closely and got some screen Shots, As soon as the Car leaves after getting its Heated Steering Wheel installed, the Slot Sends a request for Steering wheels. 6 show up, the next car enters the station, the requirements change for the next car, then I get a refund for the new steering wheeels it just asked for. Then it requests 6 more, I can email you this savegame if you want. Hope these screenshots help.
This may wwell be a more fundamental error by the stockpile. It doesn’t know for sure what the next car will be, so it doesn’t know it will be needing heated steering wheels, so it pre-emptively orders regular ones, then immediately realises its error and throws them away (you get a full refund BTW) and orders the right thing…
Fixing this is non trivial, because it either means the stockpile has to decide which car is coming next (almost impossible), or maybe…it should copy what the last car did… I need to think about this…
Ultimately I could just add a Straight section before each slot, outside of the loop and see if that helps. Or I could stop making loops. 
It still wont know what car is coming next, I really should recode it to use the details of the last car it actually worked on…