Honestly if you want a little HP gain, your talking intake($350), custom ls6/ls1 intake manifold ($350-500) Cut out or full exhaust ($50-$1000). Down pipe ($150-300), Dyno tune or downloader ($200-500)

Or car tuning turbo kit for $5600 with intercooler, cutout, injectors, tune, water meth, shift kit, everything you need.