Yep, it does seem to have a very nasty stall. I really don't know enough about it's real performance to discuss if something is wrong; however, I have found that nasty stall characteristic has been helping me learn how to use the Kitty the way it should be used.
The Kitty is a really good E fighter! Having to keep my speed up to avoid that nasty stall has forced me to treat my Kitty right and keep her fed well with E. Keep her fast and treat her right and she'll reward you with many kills.
Still, it would be nice to be able to push her a little harder when the fight degenerates to a stall-speed turning battle skimming the wave tops.
Kitty purrs, but if you stall her she'll demonstrate that she has claws.

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Lephturn - Chief Trainer
A member of The Flying Pigs
http://www.flyingpigs.com "A pig is a jolly companion, Boar, sow, barrow, or gilt --
A pig is a pal, who'll boost your morale, Though mountains may topple and tilt.
When they've blackballed, bamboozled, and burned you, When they've turned on you, Tory and Whig,
Though you may be thrown over by Tabby and Rover, You'll never go wrong with a pig, a pig,
You'll never go wrong with a pig!" -- Thomas Pynchon, "Gravity's Rainbow"