The most common answer regarding a FI motor is it will do nothing. As I understand it they were designed to allow more complete fuel/air mixture before entering the cylinders on carb'd cars. Since the mixture takes place within the cylinders on FI vehicles they do not offer any better "mixture". The only thing they can do, and the performance impact is debatable, is improve the airflow characteristics as the air passes through the intake. FYI, I have one on my 3.9l that came out of a cash-for-clunkers at no cost to me - seemed to change the throttle response a little, but it might be in my head, and there was no dramatic performance improvement, verifying the common answer. I'm an engineer though - gotta test these theories myself...
Conclusion, I wouldn't purchase one expecting improvements in a fuel injected system.
Hope this helps.