What are some good cost effective performance mods to upgrade my 05 350z?

[danielwebb]

hey guys I just bought a 2005 350z and Its awesome. I would like to add between 15 and 30 horsepower to it though. I want to do this without spending a ton of cash and without compromising to much gas mileage and deffinitely without compromising reliability. Any suggesstions would be greatly appreciated. Also if you could include the cost of your suggested mods (installed cost if i need a shop to do it) and the amount of real world horsepower it would add i would appreciate it.

Thanks