My Toto ST 424E emax is making the "barking" or whistling sound at the end of the flush. From advice on this site, I got a Korky 528 valve cap. The instructions talk about removing the Toto cap by pinching the float arms. I've seen the youtube video from Korky, but the Toto cap looks different. The cap on the Toto doesn't have pinchable float arms and I am hesitant to push too hard and break it. I've attached a pic. Anybody have advice on removing the original cap? Thanks.