Hey XterraMike
I want you to try this, next time you fuel up, put 1 to 2 cups of ultra low sulfur highway DIESEL fuel in with your gas. This will lubricate your fuel which is what the leaded gas used to do and the unleaded gas used to do with out the ethanol. The ethanol robs the fuel of its lubricating properties.
You will feel more power, perkier gas peddle, better fuel economy and smoother ride.
I have tried this so it's okay, you will not be hurting your Xterra.
Fuel injector cleaner is made of ultra low sulfur kerosene. Kerosene is refined diesel basically and what is ran in the winter in oil furnaces.
Today's diesel is so clean you can use it to clean your injectors and it is WAY cheaper than paying for Chevron or STP every time. This will lubricate your fuel system, clean it, and possibly clear Check Engine Light. Please try it let me know how it went. Pass the word!