What was found
BOI - DEICE PRESS CAUTION LIGHT ILLUMINATED IN FAST, SLOW AND MANUAL. LEFT INBOARD TAIL BOOT LIGHT TOOK 5+ SECONDS TO ILLUMINATE, BUT EVENTUALLY WOULD ILLUMINATE FOR A SPLIT SECOND. ALL OTHER BOOTS OPERATED NORMALLY PRESSURE WAS GOOD FOR ALL CYCLES. DIVERTED TO BOI, ACCOMPLISHED A UNEVENTFUL LANDING. C/W FIM TASK 30-10-00-810-801, NO CURRENT FAULTS IN CDS. INSPECTED LT INBD HORIZONTAL STAB BOOT FOUND BOOT NEEDING REPLACEMENT. REMOVED AND REPLACED LT INBD HORIZONTAL STAB BOOT IAW Q400 AMM TASK'S 55-13-00-000-801 AND TASKS 55-13-00-400-801. OPS CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.