Turbo Speed for each EcoBoost engine needed

I'm curious if anyone has a list of max turbo speeds for max efficiency for each Eco engine. I've been trying to keep the turbos on the 3.5 to about 225K. If you go above that they seem not do as well. Was curious if anyone had this info for the other platforms. Thanks

Turbo speed is inferred but I found that the efficiency goes downhill above 5200 RPM engine speed or so when you raise the boost.