As you may figure, I have a big ass straight line, and I'm just trying to send a bot down it side by side with me at 200-250+ mph while chucking 44 pounds of boost at some poor malaise era v8's. How do I do this?

[1] set that AI uses player colors and setup
[2] go in single player and select your track, car and car setup
[3] join race - with your car
[4] add AI
[5] leave race - only your car, leave AI
[6] start race

Then an AI path generation process should take place. When it's done a *.knw file will be generated in some of LFS data folders and a race should start. I'm not sure what are the requirements for your layout, it has to have some basic references like start end and maybe something else, not sure.

The .knw files can be generated ONLY in standard LFS tracks,no open configs,no custom layouts. So your best chance for straight line is the 400m (1/4 mile in your weird currency ) drag strip or Aston/Kyoto/Westhill long straights.

Isn't there some kind of object one can place in a custom layout that AI's can use for path generation? I remember in cs 1.3 and latter there was some kind of bot checkpoints one could place there must be something similar in LFS. I mean, what makes a standard track different than a custom one, with regards to AI?

No,there is nothing. Why exactly nothing has been developed to give AI opportunity to learn new tracks has to be answered by Scawen himself - he knows the process behind the scenes,I just know what is currently possible and what is not.