my car idles real jumpy when i slow down and stop at a stop sign or a light and after about 15 seconds it will stop, or i can rev it up and it stops

what could this be?

have new opti,wires,plugs,coil,fuel filter

Note: i just put headers on my car and didnt change the OXYGEN SENSORS.
COULD THIS BE MY PROBLEM?

all help is appreciated

 

could be bad gas, could be that yr tb is dirty inside, just get some tb cleaner and clean the inside really good, always start with the simplest things first, my idle jumped a little, cleaned the tb runs smooth now