Years ago, Blow BY Racing was the first S197 I ever read about (Johnny Z I think he was), to completely rebuild everything in his motor which sat in the first LNR body kit to boot.
He was very dissapointed in the fact he could barely crack the 400HP barrier. I think he actually only got like 380 or so RWHP.
The costs invested were alot.
FI is the best bang for buck period.
Besides, when you sell car (IF), you simply unbolt it, sell both seperately and walk away.
Don't want to talk anybody out of any mods, everything is cool to do depending on needs, just be aware of point of diminishing returns.