Best "BANG" as in performance gain? Ie seat-of-pants FEEL?
Warranty-friendly? Good value overall?
--- Ring / Pinion swap. Go w/ 3.55. Under $600 total for cryo+polished gears, a speedo kit, and rebuild parts. "Feels" like a 16% HP boost. No mod feels so good for so little.
--- You cannot beat 10-15 HP w. hoses / filters. THATS BANG!
--- $475 for an aluminum flywheel gets your ATTENTION.
--- Headers / cat-back add 35-50 HP....cost under $3500. Hard to gain that much HP for that low cost. Bonus: SOUNDS / LOOKS GREAT .