well with only 600, i'd get a KN air intake kit and TRUE dual flowmaster exhaust, you don't need to buy the whole exhaust, just buy 2 flowmaster mufflers and 2 new cats and any good muffler shop could built the exhaust system for you for a fraction of the price of a whole catback exhaust, also an air intake kit won't help much with acceleration unless you have an aftermarket exhaust, i have a 98 K1500 Silverado with a 5.7L 350, has a KN air intake kit and TRUE dual flowmaster exhaust and i love the sound and the air intake did make the acceleration a lot better, also the filter is washable and reusable so don't need to buy another filter, but you need the exhaust to with the air intake for an air intake to give the better acceleration, if the engine is breathing good in it need to breath good out also, it would be like you taking a deep breath in but a little breath out
