So why only in that rpm range?With the white residue on the plugs, you definitely have coolant leaked into cylinders.
The hesitation at 3K RPM is caused by the plugs being fouled up and not sparking.
This is a serious problem. I suggest you bring it into a good Toyota dealer for diagnoses.
If leaks are confirmed, you can try to use the radiator leak plug fluids. It would help.
I'll get a head gasket leak tester. That should tell me if coolant is entering the combustion chamber.