04 silverado/ vortec 4.8/sluggish low end while towing/chip or engine tuner

[400smallblock]

my 04 silverado extendwd cab with 4.8 runs good except when i tow my 24 ft rv camper. it weighs 4000 lbs. at highway speeds while in tow/haul trans mode it pulls good. my problem is dead starts from red lights or stop signs when i need low end torque. it kinda bogs and has no real power untill about 2500/3000rpm. i know one thing aginst me is cubic inches. my little motor wont have tons of low end power/torque. but should have more than what i have. i saw on another site that gm has a system that retards ignition timing at low speeds when gas pedal is mashed. this may be some of my problem? what do you guys think? i also saw guys installing chips or engine tuners. they say they really work well. they reprogram or bypass the ignition retard feature and fuel/air ratio. suggestions please