it may be your throttle body...my buds G35c did the same thing and he had the throttle body replaced...its a known issue and is covered under warrenty...id get it chkd out...

 

and why is that?

 

same thing happened to me when i would drop out of 6th gear the car would die and if i started it warm while running errands, same thing, low idle then die. this all happened after i installed my plenum spacer and had the ECU reflashed. i did the idle reset and it fixed the problem.

 

well, I had my battery unplugged for a couple hours since I replaced both of my ballasts. Now the problem is back, I'll need to try to reset again tomorrow! Im going to clean out the TB and MAF this weekend.

edit: I should mention, in the past my G has almost left me stranded and wouldn't fire up at all for several minutes or hard cranking.

edit2: I also had my battery checked, it was rated @ 410 crank amps

 

Some TBs have sensors or coatings that can be damaged if the wrong solvent is used. TB cleaner is guaranteed to be safe for all TBs.