I know when you go turbo you need to upgrade the size of your exhaust piping. Do you have to do the same when using nitrous, since its a form of forced induction?

 

Wrong all around. You don't even need exhaust piping, strictly speaking. You don't need to upgrade the size, unless you want better efficiency/more power. Nitrous is not forced induction. Unless you are already wringing every last horsepower out of the car elsewhere, and/or have money to burn, nitrous alone is not a reason to "need" to upgrade your exhaust.



But every little bit helps.