If you fly a build with PTL & Advanced sensors, if you choose to perform your action before your manuver and then use PTL, does the stress get applied to your ship before your move or after? I'd like to know due to whether the stress would then make a red manuver that you had dialed in illegal or not. Also, would like to know that if you planned a green move whether that green manuver would immediately clear the stress token.

The stress is applied when you resolve Push the Limit, which is before your move in this instance. Thus any planned red move just became illegal and you would instead default to a white 2-straight*, and any planned green move will clear the stress.

* Note that this can be used on purpose, for example to "abort" a K-turn your opponent just blocked.

PtL/Adv Sensors and a Green Maneuver is a great use for Etahn or Corran when combined with a generic R2 Astromech. Stupidly expensive, but fun to play in a casual match.