question 2 of the night on headers

[1gengsxz3]

so i want to turn my exhaust from catback to turbo back so i was wondering some good headers for my 91 gsx also if i want to make it 3 inchs all the way does the headers outlet have to be 3 inches can a 2.5 fit onto a 3 inch down pipe?

 

[diablos991]

The "header" (singular since the 4g63 has one head) or exhaust manifold is before the turbo. Therefore to have a turbo back exhaust, no upgrade is needed in that area.

To change your catback into a turboback, you will want a new O2 housing, a new downpipe and a high flow catalytic converter or a test pipe.

An upgrade to your exhaust manifold is optional, however, I hear that the evo3 exhaust manifolds flow nicely.