The secret exit you want is located in Forest of Illusion 3. Right before the Goal Gate there will be a tall green pipe. Enter that pipe and you'll see a key and keyhole under some blocks. Break the blocks to get the key and access the keyhole.

• Yoshi's Island Forest Of Illusion 2017
• Yoshi's Island Forest Of Illusion Lyrics

• 1Normal Exit
  • 1.196 Exit
  • 1.2All Castles
  • 1.3No Starworld
  • 1.5No Cape, No Starworld
• 2Secret Exit

For all the wings strats, it is important to pick up the shell with right momentum before each attempt at the dupe. It is also important rub up against the block, but not hold right when throwing the shell.

96 Exit

No Wings

Wings

All Castles

No Wings

Wings

Spit out the red shell as the left side of the midway goes offscreen in order to line up correctly for the green shell.

This strat causes less lag, but is more difficult.

Key Wings

These wings are between 1 and 2 seconds faster than the normal version.
The most difficult part of this version is picking the shell up with leftward momentum. Being too far left will have the shell not bounce on the ground and too far right will drop yoshi in the pit, and lastly, depending on yoshi's bouncing, it can be tight to not land back on yoshi after dismounting him. The wings are invisible because the sprite slots are full in this area, while the sparkles still show up since they aren't sprites.
One last thing to note is there can be a variable amount of lag depending on the score, so score manipulation is recommended, although not required.

No Starworld

No Wings

Eat the shell at the midway to reduce lag in the rest of the stage.

Wings

Grabbing the green shell for these wings can be hard to time.

Key Wings

Same as in the All Castles version, but with a different setup for the shell spit.

95 Exit, No Cape

Grabbing the flower is only worthwhile if you are already fire mario, or have no powerup.

No Cape, No Starworld

Normal Strat

Grabbing the flower is only worthwhile if you are already fire mario, or have no powerup.

Yoshi's Island Forest Of Illusion 2017

Backup Strats

Yoshi's Island Forest Of Illusion Lyrics

Skipping the fire flower powerup transition saves a little time. Spitting the shell into the hammer bro at the end stops him from throwing more hammers and sets the shell up in a good spot to be used to boost up over the wall.

Wings

These wings are harder and save less time than their cape counterpart.

Small Only

96 Exit

The slower yoshi mount from the Normal Exit, No Wings video above can be used as well. The dismount jump at the end saves about a quarter second of lag over a normal jump.

95 Exit, No Cape

Small Only