i push the gas to speed up it doesnt want to

What is your question?

It occurs when i am in 1st and 2nd gear most of the time soometimes 3rd gear too. I tried everything from checking the catalytic converter to O2 sensors to a gas filter and an air filter. it mainly sputts or hesitates in those gears around 3500 rpms untill u jump on the pedal (not literally) and it finally catches and speeds up normally.. What do u think it may be?