hey yall i have 1999 silverado ex. cab with eldlebroch headers, pulley, k&n setup, MAFS, thermostat, 2 chamber flowmaster, hypertech programmer III, and a hotchkis 2"4" drop. right now i am running a 15.1 at 91mph. my best is 15.000 at 89mph. well i was wondering if anybody has done those free mods, like the egr valve or port the throttle body, or anything else. did they help out any? any problems afterwards? thanks yall...