Yaris 1.0 2008, engine losing power

[vitz123]

So i am suddenly having this issue with my 2008 Model VITZ/Yaris (1.0 Japanese Version), that when i press the gas pedal hard to accelerate fast from idle, the engine RPMs drop and the car doesn't accelerate, the engine sort of dies without cutting out entirely. same is when going up steep slope, the RPM's die down and the car almost stops going uphill. what could be the issue. i have recently changed the engine oil, cleaned the throttle body but no improvement.

The car could get to high speeds accelerating but when you demand sudden acceleration the car just makes a lot of noise but the car doesnt go any faster, but now the issue has gotten worse. the car barely goes to 40mph and with ac it is even harder. Its like there isnt enough power. the engine seemed perfect and powerful until this issue. the car revs high when idle. but when the car is running and the gas is pressed the car just screams a lot but the RPM's dont rise above 3500 and the car doesnt accelerate at all from the current speed. It is only possible to accelerate very slowly on a soft gas pedal.

I recently cleaned the throttle body of the car and i replaced my CAT converter some 10000 miles ago. the engine is fresh. although the model is old. the car has only 60000 miles on the odo meter. i maintain the car carefully.

Kindle suggest the possible issue/s my car might have. Thankyou!