In reading this question (Limiting factors of liquid rocket engine thrust), it prompts me to ask if there is an upper limit in how fast the propellant/oxidizer can be pumped into a combustion chamber and still achieve proper combustion? I would think that at some high velocity that the flame front (the point at which combustion actually takes place) would not be able to keep up with the speed of the propellant flow. This would then start to push the point of combustion out of the ideal combustion chamber position, leading to less thrust, possible higher stresses in other parts of the combustion chamber or exhaust nozzle, etc.
I would guess that it would be different depending on the fuel used (i.e. hydrogen vs hydrocarbon), and that it would also depend on specific chamber and injector design, but I haven't been able to find any suitable information in this specific question area.