Exhaust piping size?

What is the best size exhaust piping for my 92 (B18a1) LS Teg engine? I have had many people tell me many different sizes. Stay same as stock, go 2", go 2"1/2’, go 3". Now I figure if I go to big, It will not create the necessary back pressure our engines need. :shrug: Any info would be great! :smiley: