What was found
AFTER LANDING, STRONG ACRID SMOKEY ODOR IN COCKPIT. AFTER ENGINE SHUTDOWN, SMOKE PRESENT IN COCKPIT & CABIN. ACFT COMPLETELY SHUTDOWN, SMOKE LINGERED FOR ABOUT :15. ALL SYS OPERATED NORMAL. ACFT CHECKED, NO ODOR NOTED, RAN ENGINES INDIVIDUALLY & NOTED NO ODOR. SHUTDOWN ENGINES & TURNED ON APU AIR. NOTED IMMEDIATE ODOR & SMOKE IN CABIN AND COCKPIT. SHUTOFF APU AIR & SMOKE DISSAPATED. BOROSCOPED APU & FOUND OIL IN INLET. APU REMOVED AND REPLACED IAW MM 71-00-00.