I think what most people consider a Cat-back system is the exhaust system from the cat back to the tail pipe. Personally I wouldn't consider changing the cat-back piping without also changing the cross-over too (the real restriction) and putting on headers.

93 4X4 ext-cab, auto, SR5, 3.4 V6, supercharged, 2.1" pulley, URD fuel mods, Aquamist WI, IPT valve body mod, dual cases, 4" superlift, Alcan springs, 33 BFG MT, ARB locked front & rear, 5.29 US Gears, RB 1" BL, 1.5" BJ spacers, TJM T-17, Warn m8000.