downpiping and headers are the exhaust system in yr car ....
2 inch piping is size of yr car piping where as stock is around 1.5 ....
2 inch piping is big enough for this engine you batter go for 1.75 with some fueling improvements...
if you dont have enough fuel coming in and letting more gases out quickly will not benefit you at all....
plus you will have less pick and more top speed improvement