Has anyone added the components for Adaptive Cruise Control to their non-tech RL to add that feature? I imagine the wiring harness is present. Is it possible to buy the components to plug and play?

 

I suspect it won't be possible. I have the tech trim, which has CMBS. Here's what you'd need:
Radar unit behind grill
New grill with radar shield
New steering wheel with adaptive cruise follow distance button
New dash to have a CMBS Off button.

 

What a project, but hope you can get it done.
This is the one feature I really want that's pushing me to buy a newer car, but things are so expensive right now.

 

you'll have to get new computer unit and abs/vsa modulator assembly ($2100). extremely complex. This is for the 05-12 RL. for the RLX it's even more complicated with camera units all the belt and whistles, might as well get a new car. You can try to get a crashed car and part it out, but even this option is too much trouble (crashed car with cmbs harder to come by. calibration is a headache).

 

I think the above posters are correct. This question has popped up on this site before, and it's definitely not anything resembling plug and play.