i bought an 04 rc a while back with less than 3000 miles and the boy put a k&n drop in filter and a complete magnaflow exhaust still has manifolds,no cats and a tuner laying in the glovebox.he bought the last two directly from roe.my question is how do i know what octane the three different levels require.it shows a low,med and high tune.oh yeah the thermostat is a cooler one,other than that truck is stock.thanks for the help.