i think stock exhaust is 2"
i went with a 2.5"inlet, 4"outlet BOMB straight cylinder muffler w/silencer, 2 1/4" piping and took out the convertor. it sounds pretty loud without the silencer but with the silencer it sound sweeeet. the car feels faster too. i recommend this setup for street racers. all i need to complete the exhaust system is a header.