How can I increase the total performance of my car?

I have a 2003 GMC Envoy and I've stripped all the extra weighty things off of it (spare tire, running boards, luggage rack, back seats lol) and i've also added STP fuel injector cleaner, STP fuel system cleaner, Octane Booster, Rislone engine oil treatment, a K&N air filter, and I'm going to be installing a Purolator Fuel Filter and Bosch Platinum+4 spark plugs. Will the spark plugs increase my acceleration? And what else can I get to increase the acceleration because my truck is really fast, it just has a slow start up from like 0-20, but after it hits 20mph, it takes about 2 seconds to get to 50mph, and i'd just like to increase the "off the line" time without spending an arm and a leg.