Salvatore,
If you're looking for the least amount of hassle, easy installation, most reliability, and only looking to spend in the hundreds, I would only do intake and exhaust.
Check out my optimized AEM intake setup.
http://forum.mazda6club.com/engine-drivetrain/189329-aem-intake-users.html
I remember when I first bought these, they were over $400
Mazda 6: Cat-Back Exhausts: Power Pulse Exhaust System - 03-08 Mazda 6 -
If you're looking for the least amount of hassle, easy installation, most reliability, and only looking to spend in the hundreds, I would only do intake and exhaust.
Check out my optimized AEM intake setup.
http://forum.mazda6club.com/engine-drivetrain/189329-aem-intake-users.html
I remember when I first bought these, they were over $400
Mazda 6: Cat-Back Exhausts: Power Pulse Exhaust System - 03-08 Mazda 6 -