custom exhaust size??
 

i have a '99 2.8 quattro and im looking to do a full exhaust. i have the cats and muffler figured out but im looking for the best size to use ?? 2-1/4 or 2-1/2? om looking for better efficiency of flow for the most part... sound and power are pos. side effects... does anyone know here i can get some headers?? is it worth it? thanks
( if i may have missed this somewhere else here... oops)

what size is working best?? what are you running??