Hi Flow Toilets

[branchacctg]

There is an American Standard ( don't remember the model) that has two drains from the tank into the bowl. I presume that would give you the flow that you need.

[MstrCarpenter]

These just work! Don't let the kids watch the video.
https://www.youtube.com/watch?v=3qeK_SoPGHM

[Willyou]

I installed two of the American Standard Champions recently. Neither of them worked as advertised unless I held the handle down for a couple of seconds or until I raised the water level about 1" by extending the overflow tube and adjusting the fill valve. They make a little different noise when flushed, but they work well now without holding the handle down. I understand that you can get replacement flush valve assemblies that are similar to the old flapper valve system but larger. These apparently work better, but are a significant extra expense.

[Willyou]

I installed two of the American Standard Champions recently. Neither of them worked as advertised unless I held the handle down for a couple of seconds or until I raised the water level about 1" by extending the overflow tube and adjusting the fill valve. They make a little different noise when flushed, but they work well now without holding the handle down. I understand that you can get replacement flush valve assemblies that are similar to the old flapper valve system but larger. These apparently work better, but are a significant extra expense.

[sleepy hollow]

Might also look at Toto.  I have one that is 20yrs old.  The low flows were still scaling up when I installed the Toto.  The other brands were not getting good reviews.  Lots of complaints and dissatisfaction at the time as I recall.  After doing a lot of research, I ended up with a Toto and it has never clogged.  It also does a decent self cleaning job, but nothing like the old days when we were free to buy products designed for our comfort, not for assuaging the delusions of the bureaucrats.  

I do not recall the model but it appears to be the Drake 1.6g version.   Not the one-piece tank, but the two piece design.  Only ever had to replace the gasket in the tank and the handle which just disintegrated one day.  Would definitely buy it again.  I still have two of the old-school toilets.  Frankly the Toto has been more reliable and less prone to clogging I have to say.