hello all i am new to the forum and need some help. i just bought a 1998 buick century with 92,xxx miles. when i try to start it i have to push on the gas to get it going and it drives great. but when i get to work and am idling it gets really rough and seems like it wants to cut off. i have replaced the air filter, fuel filter, air charge temperature sensor and the idle air control valve. i have also thouroghly cleaned the throttle body. im running out of ideas and any help is appreciated. thank you.

Did you replace the spark plugs (gapped properly?) and k ohm test spark plug wires?
Spark plug condition (when u pull them) can tell how car is running..

Any engine codes?

plugs or maybe fuel pressure regulator, which can be tested by sniffing the vacuum line for gas if present its bad or check koeo fuel pressure, should come up and stay there not fade off