brand new to this so im full of questions.i have 2000 2500 silverado with 6.0 4l80e 4x4. its got cai, true dual exhuast, shift kit with 30in. tires. my first question is about the O.S. im thinking i should be using the 1bar. just kinda scared to mess things up. if anyone will walk me through this i would greatly appreitte it. my real problem is the shift from 4th to overdrive. but ill get to that later. PLEASE HELP