A 4" exhaust and a free flowing air filter like a K&N or Amsoil in the stock location or even better, a Psychotty or RE-0880 will definatley help with power, lower EGT's and improve fuel economy. None of those items will void your warrantie and are easy to install and will cost well under $1,000. Thats all i have in my truck and it FLYS and i am getting 20MPG give or take and its not even broken in yet. Ill leave fueling box suggestions to other members who have hands on expierience with them
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01' Intense Blue 4x4 QC SB Auto, Black Leather, Camper/Tow package, etc, etc. JRE Exhaust, Psychotty, Autometer Sport Comp: Trans Temp, 0-35psi Boost and Pre Turbo EGT Gauges, Rhinoliner, PIAA 520 Fogs, Stull "Diamond wire" grill, Westin Stainless sidebars, Smitty bilt "Outland Sport" stainless bumper guard, Hella B/U Lights, Tint, Pioneer audio, JL Audio 12" Sub in center seat. SEAL TITE crossover box. Amsoil dual bypass with the "CPFF" Adaptor and braided stainless lines, Husky liner mudflaps, Motorola Spectra Locomotive radio, Whelen 100watt Electronic air horn/pa. Mag-Hytecs Soon.