Which exhaust makes more power?

Originally Posted by theDreamer

Correct, putting an exhaust on a Nismo will probably net equally to slightly smaller numbers because of the more aggressive tune a Nismo already has. Everything else about the cars are the same engine wise, minus the exhaust & tune.

Edit: To answer the main question, I think a lot of Nismo owners are first changing to HFC/RTP to open the exhaust up.