LS3 or L99? Typical first mods are a cold air intake, (Cold Air Inductions system typically has the best results as far as power and IATs) and a decent catback. Are you worried about a warranty? These engines LOVE mods. Any power level you want is obtainable. What Throttle Body mod are you talking about, polished throttle body?? Not worth it. Guy down the street from me has 1300whp and using a stock throttle body and intake manifold. I have this sub box in my trunk, saves a lot of room. Welcome to the forums!