4263 on the S79 was interesting. It was tremendously fast for a hybrid and absolutely hauled ass up the Verrazano, so I assumed it was really well taken care of. It might actually be in shitty condition under the hood, however. It kept making that all familiar pop-off valve sound (I know there's other air release sounds, I'm talking about this specific sound we all know and love), and I've literally never heard an NYC hybrid bus make that sound. Odd. Any ideas?