2" Exhaust to 3" Pipes?

[Canuckr]

92 4Runner 3.0L 4WD

Stock muffler and cat
Upgrading muffler and taking my catalytic converter off, live in Canada and dont worry about the emission tests here. Looking to get that little HP and MPG gain. Have a K&N cold air intake.

Can i get some advice about changing exhaust pipe size, i have 2" exhaust and want to go to 2.5 or 3" ... would it help, or not do much, or be worse? I am not changing the headers, so should i stay at 2" exhaust?

 

[Wizzard]

3" is definitely too big, you will have a drastic decrease in back pressure and a likely decrease in torque, 3" is suited for 700+ HP applications. I would just keep it at 2" since you are upgrading the muffler already (assuming it is more free flowing). Headers would be the main restriction (not meaning that they currently are a 'restriction'). Hth.