Two words: TOTO DRAKE
I lived in an appartment where the landlord, in his infinite wisdome, replaced the original
pre-ban toilet with a low flow model. Damn thing plugged up every time.
Luckily for me, it was an old design with simply a plastic baffel inside that limited the
volume of water that would empty into the bowl. Nothing some cutters wouldn't fix.
Then 8 months ago, wife and I bought a home.
While remodeling the bathroom, I managed to plug the toilet.
Screw that. I did some online investigating, and found that professionals seem to
all agree on one brand. Toto.
Specifically, the Toto Drake.
Toto is pretty much the world's best manufacturer of toilets.
The Drake is a USA legal, post ban 1.6 gallons per flush model.
It has a huge 3" trap.
It uses a standard design flapper valve, although it is twice a big as your toilets'.
My parents have the American Standard Champion, which is similar except for a different
type of tank valve. The Toto, in my opinion, is much better.
I have not seen the Toto Drake in any stores.
I had to buy mine from a place that cators to plumbers/pipefitters.
If I remember, Toto has a distributer locator service.
I installed it myself.
Advice: Toss the supplied tank/bowl attaching hardware,
and pick up the same type of kit available at Menards.
The factory supplied washers are rubber, and squeeze out of place.
Menard's kit has fiber reinforced rubber washers which don't squeeze out of place.
OR, pay a plumber to do it for you so they are liable if your basement floods.