I have a 2001 kia sportage 4 cyl ... a few weeks ago i had a warning light come on telling me there was an ?

I have a 2001 kia sportage 4 cyl ... a few weeks ago i had a warning light come on telling me there was an emissions issue w the car ... the light eventually went off and I took the car to Auto zone and they said it was a small vacuum leak somewhere but was insignificant.. in the last few weeks my car has begun to sound more and more like an Old VW bug engine (like a cycle) ..anyone know what is causing it?