True Blue Racing

I have a misfire. Im trying to figure out the cause and cylinder that it is located in. The check engine light is not on, and i had them scan for pending codes and there wasnt any. what is the best way to find out what cylinder is misfiring. I can free rev the motor with no miss. once the motor is under load tho, anytime that i go TOW or even 3/4 throttle it misses. Anyone have any insight.