Goran replied:

Tony , 2 1/2 in is more than enough for you motor . Just make sure the flat spot in the tail pipe is by passed with the new system .

colin replied:

Hi Tony, dont fit the free flow muffler unless you like heaps of noise in the cab, i fitted a ford v8 stainless muffler which does the job well. Col.

Yonnee replied:

Normally with turbo motors, the bigger the exhaust, the less back pressure, the more power (to a certain extent).
Ask whether your local guy can do mandrel bends. If so, a 2.5" mandrel bent system will flow almost as good as a
normally bent 3". (the normal bends kink the pipe) Also look at the difference between mild and stainless steel.
The stainless system will never need replacing due to rust, however in severe off-roading, landing on a rock can damage
the pipe leading to another expensive repair as not all places can weld stainless.
Cheers,
Yonnee.