5-8 team...if the UTEP loss doesn't happen. That UTEP loss probably kept the Cougars from a 3rd straight Top 10 season (#7 in 1983, #1 in 1984, #17 in 1985).
BYU's only other losses were a pair of 3 point setbacks to:
#7 UCLA (Pac-10 Champions and Rose Bowl Champions)
#14 Ohio State in the Citrus Bowl--which was a Top 6 Bowl game (Ohio State knocked off multiple ranked teams including #1 Iowa in November)
BYU had key wins over Boston College (28-14), Washington (31-3), and gave eventual #5 Air Force (they were ranked #4 when we beat them) their only loss of the season (28-21).
1985 Air Force was really, really good. Probably their best team ever. They blitzed through the WAC beating teams like UTEP and Wyoming 49-6 and 49-7, won the Commander in Chief Trophy by a combined score of 69-14 against Army and Navy, beat old SWC team Rice 59-17, got past #15 Notre Dame 21-15, and ended the season by beating Texas in their bowl game on New Year's Eve, 24-16.