[dre5491]

On the exhaust part you should be gaining more than 2 hp. If I were you I'd still get one because if you plan on modding the engine in the future a good exhaust with all your other mods and a right tune you'd notice more than working on the engine and not changing the exhaust. Deff change the retainers and valve springs like beaters said. But no doubt, if you plan on performance throw some forged pistons in that too. Get meaty injectors and a fuel rail for better fuel flow. Then the next route to go would be forced induction or adding in some spray. I would personally rather have boost than spray but thats just me...