Hesitation under 2k

Hey all. I have a 2000 cavalier z24 5 speed 106000 miles, with some hesitation issues. It seems to only happen when i am on the throttle like casually going through 1st, 2nd and 3rd. The hesitation only happens under 2000rpm. Once im at cruising speed it wont hesitate at anytime. I have had codes P0420, P0137 and P0442. I know what these codes are but i cleared them to see if they would come back and so far after 50 miles they havent. I have searched for this issue but with no avail with this specific situation. Thanks in advance. I hope it all makes sense lol.