I 2nd the two stroke oil suggestion. The white smoke wouldnt indicate a bad FPR, the rolling idle could. Does it sound loud at idle...and what I mean is the injector "knack knack knack knack knack.." Is it louder than other LB7s you have heard? If your FRP sensor is bad, it could be adding too much pressure at idle which makes the injectors loud and starts to F up a smooth idle. My 03 is quiet at 35kpa idle rail pressure, my 01 is loud and has a rough idle, if I turn my rail pressure down, it quiets up and smooths out.
And someone else chime in here, a cracked injector wouldnt neccesarily show a bad balance rate. White smoke says your getting too much fuel at idle... so either leaky injector (cracked, bad seat, whatever) or FPR sensor.
Start with the bottle of 2 stroke.
2004 CCSB AFE, Banks Exhaust exhaust, 6in Lift on 35's
2003 CCSB Edge Attitude, Banks Kit, Lowered on 20's