QUICK question about exhaust piping

what is the stock piping size on a 93 rs coupe and i know 3." is to big if you dont have a turbo but if i go with a 2.75 will i still have enough back pressure . i have a tusuto n-1 can and wanted to upgrade but everyone tells me to just keep the can and upgrade the piping . will it be similar to a cat back?? tips and help greatly apprciated thanks!

a cat back is all the piping after the cat to the tips. so if you change that piping you’ll basically have a catback. however for your piping size, whats your engine setup??