The intake +ubend delete would probably help you pick up a little gas mileage. Hell I went from 18mpg on the Hwy to upwards of 36mpg Hwy with my mods...
Taking out the U-bend is simple, and a great mod, but as far as visuals go, you could always yank out a few panels (dash, center console, armrest, etc) and take a can of paint/clear to them, makes a world of difference.
I wont get into any detail with audio, but if you know it, then you'll know what to do, if not, then dont worry about it.
You could always take some sand paper to the exhaust tips and make them shiny, always looks good.
