In this route I completely ignore the "Psionic Whistle" powerup, which let you summon the kitty after you throw her. Route is changed accordingly to the lack of this powerup, but only the key-5 section is much slower because of it, in the rest of the game I don't see any real advantage to having the whistle (Maybe except the Blocko boss, having to collect the kitty for the last hit is a loss of 2-3 seconds)

In conclusion, lost time from the optimal possible split of key-5, but time save on the whistle is (hopefully) bigger.