94 sonoma rough idle /'exhaust leak?

Hi ok after forever trying to find a 89-93 sonoma s10 we gave up baught a 94 4.3 high output rough idle salesman said it is the exhaust leak near the flange . would a exhaust leak cause a rough idle ? sorry we don;t know anything else yet we haven't got it on the road to see if idle clears up also the tack says between 1k and .5k back and forth for the idle at start up thanks to the people of the bbbbbbbeast website Stiletto