well i've never actually heard of spiralmax... but i'm guessing its some sort of throttle body modificiation. i used to have a poweraid
throttle body spacer on mine... which also was supposed to create a "vortex" of air to give better power, torque, gas mileage, etc. i noticed a little difference, but nothing huge. i wouldn't pay more than $40 or so for an upgrade such as that. you wanna make a real difference... put a new airtube on there with a K&N cone filter.