THE ACFT WAS ON A SCHEDULED, DOMESTIC, PAX FLT. THE COPLT WAS THE COMPANY'S CHIEF PLT AND WAS FLYNG THE ACFT FROM THE LEFT SEAT. HE WAS UNDER SUPERVISION OF THE PILOT-IN-COMMAND (PIC) WHO WAS IN THE RT SEAT. DRG ARRIVAL, THE CREW ELECTED TO MAKE A LOCALIZER-ONLY APCH TO RWY 33 WHICH WAS WET. JUST PRIOR TO LNDG, THE WIND WAS REPORTED FROM 280 DEG AT 15 KNTS. (ACCORDING TO AN OFFICIAL WX OBS AT 1736 MDT, THE WIND WAS FROM 290 DEG AT 17, GSTG 25 KTS.) REPORTEDLY, THE LNDG APCH & TCHDWN WERE NORMAL. AT APRX 90 KTS, GROUND FIND FINE PITCH (GFP) WAS SELECTED & THE ACFT VEERED TO THE LEFT. NOSE WHL STEERING & RUDDER WERE RPRTD AS NIL. THE PIC ASSUMED CONTROL, BUT THE ACFT WENT OFF THE LEFT SIDE OF THE RWY BFR HE WAS ABLE TO STOP THE SWERVE AND PARALLEL THE RWY. THERE WAS NO DNG OR INJURY. DURING AN INVESTIGATION, THE LEFT ENGINE WAS FOUND TO IDLE AT 8000 RPM, THE RGT ENGINE IDLED AT 9000 RPM. THE RECOMMENDED IDLE SPEED WAS 6500 TO 7500 RPM.