Outer Limits 4x4 Board

I know this question is answered in the bible for an SD33 non-turbo but what size pipe would everyone recommend for the for stock turbo version with out losing too much economy?

can only gain, I had a 3 inch and now run 1/2 of a 2.25 system and is fine.

The back of the turbo is only 2.5 inch anyway.

I was thinkin of a 3" system on mine. Should sound tough as.

Oh and pongo, C.K. kicks arse!