[revkev6]

a little hard to help you with so little information. what kind of motor/carb/ignition??

is it a rough idle or only when you give it gas after startup??

I had a flathead that would start and idle but give it gas and it would pop and fart horribly and it was a bad condensor.

if you have a stock 180 degree type intake manifold you may have a bad cylinder. as the venturi works on vacuum it will draw less on one venturi. do a compression test to check for this.

if it is a 97 you may have a blocked emulsion tube. these can be a real pain to remove as you have to tap them and make a puller to get them out. they can be cleaned and reinstalled afterwards or buy new from stromberg.