94Z28LS1toLT1

Hey fellas just had a quick ? A couple years ago i had an exhaust leak n the muffler shop said it was my catalitic converter so they changed it,but my original converter was big, but the one they changed was alot smaller,i didnt like that thinking of that after i did a tune up on the car.but does it matter the size of the converter,will it affect any thing in the future.and it wasnt a leaking in the coverter,just a crack in the exhaust manifold