I need Help My Car Don't go over 4000 rpm

I have a new problem with my car is it a v6 2003 model .....
the rpm don't go over 4000 rpm it act like it is on the 8000rpm ...

the car shift's when i don't push the fuel too much like normal step with rpm lower than 4000 but when i want to race or go fast i kick it and it stuck's @ 4000 ..

anyone know how to solve this problem and why this **** is happening .

it worked but come back again

hey it worked for 1 hour and after that the same problem back again...
is it a speed sensor problem or a rev limiter problem or my car computer is mixing things up ....