Unless you are going tobe super charged or major boltons eg: heads,cam, intake ect then 3" would be benificial.
If your keeping it close to stock the factory 2.5" is plenty even with long tube headers and CIA.
DYI Oil Catch Can,DYI dash ABL,DyI fender "V"emblems,ACC Plasma DRL,
DYI Painted red SS on steering wheel,
DYI CGM painted bowties on wheels,
DYI Clearcoated Brake Calipers,
Eibach pro 1" lowering springs,
GM Heratige grill,
GM skipshift eliminator,
GMPP 92206992 Exhaust
2-10" Kenwood subs w/350watt pioneer amp
RiderGraphics hood spears/gill outlines