In calculating whether or not you are legal with respect to 8 in 24, for a 135 leg, you must include all of your commercial flight time, not just your 135 flight time. Part 91 time is commercial if it's your job, or if you get paid or should be getting paid for it. If you are flying your bosses airplane, it is assumed that it is your job.

If you chose to go up in your very own Pitts Special and do some aerobatics for fun, this would not be commercial and would not count against the Part 135 8 in 24 limit.

Military flight time, such as Air Force reserve or ANG also does not count as commercial flight time.

Joe