My first engine mod was CAI kit by Volant. Installed it right before going to the beach a few weeks before...
A few months later i unbolted the muffler back portion of my exhaust, cut off the exhaust pip from the muffler that goes back over the axle and cut the resonator off. Added a Magnaflow 2.5" center inlet/ 2.5" offset outlet, added 2.5" pipe from the muffler to the portion that goes back over the axle. The pipe and axle portion i welded (not pretty but no leaks). The muffler was slid on and exhaust clamps hold it.... for now.
After CAI, Exhaust, and Spark plugs i got a used 4.7L TB and a few months later i got a great deal on a Stage 2 JET chip