it won't hurt getting it b/c the stock cat will be a bottleneck in the exhaust system...a hi flow cat will help some

on such small n/a engines exhausts help little unless the stock system is so restrictive

another thing you can do is upgrade the engine management system to take advantage of the lower back pressure created by the more efficient exhaust system (but ems systems cost a good amount of money and are not cost feasible with such few mods)