That’s the Norwall model from A-S. It’ll be hard to find a matching yellow one, but here’s a white one. I’d check EBay for a yellow one, that may be your only shot.
Unfortunately it’s not possible. The bowls that come with those pressure vessel tanks are specially designed with the high pressure in mind. Using a traditional gravity-style flush valve would barely allow a trickle of water to go into the bowl.
Looks like one of the cheapo kinds that come with new toilets. They seem to fail pretty frequently. I wouldn’t bother tinkering with it, just replace it with a new Fluidmaster or Korky brand valve ($10-15 at most hardware stores).
I just don’t understand why Toto felt they had to redesign the Drake. They have the Drake II and the G-Max, both of which work perfectly. If it ain’t broke, don’t fix it. Just my two cents.
Another thing to check is the siphon jet at the bottom of the bowl. Over time, it can become plugged with mineral deposits and slow the flush down. The majority of newer toilets have them, some older ones don't.
I recently saw a video of a Kohler toilet from Japan which uses somewhat of the same idea as the old Wellworth Lite with the exposed siphon jet pointing up into the trap. Hopefully this time they executed it a little better.
Lamosa toilets are known to be very low quality and cheap, FWIW I’d get something better. I’d say 99% of the toilets on sale today are better than a Lamosa.
Cool, an American Standard Yorkville! American Standard does still make the Yorkville, although it’s a pressure-assisted model so it’s a little louder, but performs pretty well. Kohler also makes a rear outlet toilet called the Barrington, which like the Yorkville is pressure assisted. Either...