2½" with straight thru mufflers will be big enough to not be a restriction at your powerlevel, 3"will give you a deeper tone and will be alitle louder and will give you alot more room for more power if you end up building a hotter engine in the future since 2½" with good mufflers are generaly good up to about 450Hp,personaly i prefer the sound of a H-pipe but that up to you what you prefer:)
Bigger risk with bigger pipes for ending up with alot of drone in the car at certain rpms thats why i like to stay alitle on the conservative side,the bigger pipes does have more rumble to them so to speak.
