You would not notice much of a gain if any unless you did some dyno time with a tuning company so that they could map out your air fuel ratios. Eurocharged can do this with an hour or two of dyno time.

The upgraded injectors are so you do not lean out on your top end. I personally noticed a little better gas mileage gain when I was not heavy on the pedal after installing the injectors. But this could be because I put a CAI, new TB, unrestricted the exhaust and new injectors all at the same time.

Others have noticed the better gas mileage with just the injectors and no tune but I am not sure of why this would be.

They are pretty easy to install but it is a mess and you have to have a ton of rags to soak up the extra fuel. After I soaked everything up as best as I could I let the engine bay air out in the sun for a whole day and night before I hooked the battery back up and cranked her up.

If you want, research them a bit and if you are still interested pm me and I will hook you up with my extra set.