been having the problem for a while now

usually when the car is at operating temp. when driving around 40 to 60 i lose power, ill press the gas. rpms will go up and motors going but im just blowing black **** out the exhaust with absoultly no power. sometimes while driving holding speed power will be sligtly lost then come back then go away then come back. can feel it and see it in rpms

ive checked injectors. there good. new map sensor and tps. all sensors have been replaced. under a yr old. all vacumm lines are good. check engine was showing 23. but hasnt come on in a while so showing no codes now. im suspecting the egr but not sure. the cat was replaced a few yrs ago

91 camaro rs. v6 auto