Mine is No#8 on your list IS-F - 273kw (actually the freakish 275KW run). Modifications: PPE headers only. Stock Exhaust, Intake and no tune.
Cheers
Chris
In the club Lexus forums there appears to be one LC500 with headers......... here in NSW Australia!......
link
https://www.clublexus.com/forums/lc-model-2018/864416-lc500-with-headers.html
Cheers
Chris