Keep the lower pulley stock til you really want to start modding, it isn't needed YET! I would FOR sure get a used unmarried Predator and save up to $200 dollars! That combo will give you over 500 RWHP with ease!! Hey limp1969 Stiegemeier did a Dyno test on a Bone Stock 03 Cobra and got 374 RWHP 364 TRQ, then the next pulls were simply adding their Blower Port (Not the Plenum) Eaton with the Stock pulley setup(different air filter) generating the same 9 lbs of boost as the first Dyno pulls, it screamed to 422-381, close to 50HP, NICE!!