As I read the card, it appears that Snap would take his free boost action after moving his ship, but before the check pilot stress step. In this case, Snap could execute a K-turn or T-roll, perform a boost, then assign the stress token. By that same measure, if Snap is stressed and then executes a green maneuver, he would be denied his free boost action due to the timing. Is this the right interpretation?

Nope. Check Pilot Stress is part of performing the manoeuvre unless you use Pattern Analyzer. His boost comes after.

Haha. Sweet. So it is. I'm glad I misunderstood that.

Primed Thrusters works for him also.