changing that gear will help performance but not gas.....and maybe run some nitrous to it if you want to race it someimes but not everyday nitrous will only cost you about $500-$1000--depending on what all you want with the system i believe the ls1 is good for a 125 shot but id just run a 75 or 100 to be on the safe side especially if it is going to be a street car running on street tires....you wouldnt get traction anyway so it would be a waste to run a huge shot....like hybrid ss said its all how fast you wanna go.....