has anyone experienced power loss from one of these? I know there's aabout a 20-30hp difference from an 04 5.3 and the newer ones but a stock 09 feels like a powerhouse compared to my 04 witha k&n intake and dual muffler exhaust. It feels like a gutless turd and would highly doubt it capable of towing anything heavy unless it was on flat land. It won't even break the tires loose from an off-idle roll. The truck has 51k on it. Still has orginal plugs and wires but I wouldn't think that's the problem. Does the truck need a tune do to the exhaust and intake? The MAF should compensate for it right?