I have a 1999 es300 and it wont rev past 2500 rpm whats the problem?

If you hit the Rev Limiter on a Ford, it will simply bounce the rev back down, to protect the Engine. So, no high Revs. But, you should be able to bring it slowly to a High RPM. That is normal. If there are no Check Engine Light on. You are most likely hitting the rev Limit and need to stop.

If your standing still in park it wont rev past 3000 rpm as its got a limiter on it And only revs past 3000 rpm in drive on the move.

If it's an automatic transmission the torque converter may be locked up.

Most cars have a rev limiter built in and will not let the engine goe past 4000 rpm's you may want to change out the spark plugs as often if it has flooded just once the plugs do foul out

run the fault codes and check for rpm limiter fault.

Have the fault codes read Replace the faulty units with genuine one because most aftermarket units are not set
for OEM cpu units and are not completely compatible

May not be getting enough fuel to the engine

You have a misfire, so you don't need someone to
tell you to diagnose what you already know you have

It won't rev past 4,000 rpm, because it is programmed that way,
just so you don't & ruin the engine

If you want to play--- get a car from the 1960's & have some fun

remove the aircleaner intake hose and, check the intake air control flap for free movement

if your run no air sensor it wont rev past 3500rpm as it would not richn the engine under load