There was one of us that had a problem with the throttle bodies previously on here that caused exactly those same symptoms.
The information below is from my boyfriend:
Some of these cars might have fuel pump issues as well.
Join the site below there is a direct write-up/tech-paper that describes reprogramming the ECM for your exact issue on page 1 or 2.
Site: Infinitihelp.com
http://x.infinitihelp.com/forum/local_l ... ?catid=183
Of those 3 possible issues above one of those should be your problem (unless you just have some thing as simple as dirty intake air filters or plugs).
