This faucet is primarily stainless steel and brass, where it counts, with a (mostly) plastic diverter and cartridges (some metal and ceramic in those).
Tuscany did, to try to placate me, send me a replacement diverter and hot and cold "cartridges" (the gradual on/off valves.)
Studying the whole thing, my conclusion is that there are several points of flow restriction, each of which has a modest effect, but added together a large effect. Some are essentially un-modifiable, like those cartridges.
It'd be very interesting but fruitless to know if EPA at some point imposed design requirements to defeat people who'd try to mod a faucet for higher flow.
Tuscany's customer service has been quick to get back to me and as helpful as I suspect they can be (send parts, etc.), but the CS Dept. can't supply alternate parts as none exist.
“but added together, a large effect.”
(comma added!)
tuscany is a menard’s store brand only ... store brand plumbing fixtures are a total no-go in my book ...