So I was playing in a tourney awhile back and attempted to do a koigran turn however I was not able to so because I guessed my opponents move wrong and would have overlapped. So I moved my ship back to where it would just be touching his ship without turning my ship around. However I was informed by my opponent that I also receive a stress token for it. In the rules it doesn't say anything about that. What's the correct ruling?

You receive a stress token for even attempting a red maneuver, just as you clear that stress token for even attempting a green one. Completing the maneuver without collision doesn't matter to the stress economy.

You receive a stress token for even attempting a red maneuver, just as you clear that stress token for even attempting a green one. Completing the maneuver without collision doesn't matter to the stress economy.

Ok thanks for the clarification

The rules actually do cover this, pg 17 (emphasis mine):

If the active ship is executing a [k-turn]
maneuver that causes it to overlap another ship,
instead treat its maneuver as a [straight] maneuver with the
same speed and color revealed on the dial.