You should be fine with just the upgraded injectors, given that the baseline Complete Kit comes with 52lb/hr injectors. That all being said, all of this is going to be up to whoever is doing your tuning, and would be better to talk to whatever local dyno shop that you plan on using, though with your headers and how aggressive you want to go with the kit, 55lb/hr injectors may be perfect. The gains that ProCharger quotes is on a car with headers, using ProCharger's tune on 93 octane gas.