Does it stall all the time at that speed?
Can you get it to go faster?
If you say yes to both, I would look at fuel, filter first and pump second.
Does it stall in any gear at that speed?
Can you be stopped and rev above 3000RPM and hold it?
I still say fuel system.
Filter is clogged preventing enough fuel flow to support the RPM or the pump is dying and can't pump enough fuel.