My 2012 2500HD Silverado has a throttle body performance issue and reduced power problem.the engine has no power when you punch it the goes into reduced power.the flow master muffle isn't as loud as it was so I'm curious if it could be a back pressure problem the local dealership said I need to put the stock air cleaner system back on but I've had 5he spectra cold air on it for 4 years and the muffle is 5 years old anyone run into this problem .I have new plugs ,wires,coils,new mass air flow sensor,cleaned the throttle body, the dealership is just trying to rack up some $$$ not give me a straight awnser after 600 bucks and all they did was change one oxygen sensor and not give me a definite awnser.