Since this is about Performance, let'* look at your sig:
95 riviera gen1 SC 2.55" pulley cold air intake, 18" wheels with nitto NT555 tires, flowmasters with no resinator or cat.
Future mods: camshaft,ported heads/intake/SC, 2.3" pulley,pcm, custome headers with hi-flow cat
You have a Gen3 Eaton M62 just like all 94/95 L67'* unless someone did something freaky to your car.
Is your intake truly a 'cold air' intake? Let'* look at your design and heat shield.
18" wheels are the wrong thing for a car you want performance out of.
No cat? Not only is that illegal, it'* also costing you low-end torque. Put a hi-flow cat in.
Custom headers? That'* going to cost you dearly, and probably won't gain you much. Our Series 1 manifolds are a really good free-flowing design.