Is there any DIY instruction on how to modify 19-21 rear diffuser to fit on pre facelift models?
Not sure if the existing rear diffuser needs to be cut or simple bolt-on.

 

There's some kid on YouTube that got pretty close. Gives you a good idea of about 80% of the effort needed.

I fabricated a mounting system but noticed the other day part is coming loose, so probably needs some improvement.

it's not exactly simple or more would do it. Nice thing is that it's only around $100 from Lexus for the part, so you're not out too much if you screw up too badly.

 

You are talking about this video, I guess.

 

Yeah that's it. Shows the trimming needed, but he never actually attaches it to the car. I had reached out for info and he abandoned the idea. I didn't need to heat mine like he did with the mounting solution I made. I think I saw some guys on FB said they just used foam tape to hold it. So a few options.

 

Thanks for the input and the link.
Based on the video, I was just going to bolt the bottom and tape the rest after trimming, but I guess it's easier said than done.
I think OEM looks good and subtle.