Lacking Low RPM power

Hey my 94 z28 has 160k on it... its lacking power only under 2500, but at 3000 it feels like im being slammed into my seat. So i changed the plugs, wires, fuel filter, air filter(K&n), and it cant even spin the tires if i just floor it, but after 3000rpm's ill kick out. Its really sluggish under 3g's, But incredably fast above that

maybe a transmission problem?

Did you gut your cat or do any other mods?? Sometimes gutting your catalytic convertor can hurt your low end torque.