Welcome to the Nissan Patrol forum. To post a question and to see less adds on the forum then you will have to register
first. We are an easy going friendly forum so join in the conversations and feel free to ask any questions.
Become a forum sponsor for only $20 and see no adds with faster page loading times and many extras benefits.
The 3" exhaust I had on my turbo'd TD42 GU had a redback muffler on it and was as quiet as a standard exhaust but flowed very well.
As long as the muffler you fit is not restrictive there will be no need to retune the engine.