I used to have IHE for my ls. You won't notice the difference until you drive an un-modified ls. If i could've went back, i would've difinently waited for turbo. Eventually IHE gets boring. I remember when i was doing research, I just found turbo too overwhelming with what is needed but now i wish i had my... $1200 back from I/H/E and put it towards my FI route.

I'm just warning you, wait until you've figured every route to do then choose what application you want.

ps: suspension is always an A+ idea.