I own a 2010 silverado, 5.3L, 6 speed, 3.42 rear-end, 18,000miles Wondering if anyone can hear a slight tapping, almost like an exhaust leak or lugging sound from the engine when cruising at 50-60mph @ 1200 RPM like it does? I can hear it near the floor/firewall on the drivers side. More noticeable as it change from V4 to V8. It only seems to be apparent when the truck is pulling at that real low RPM. Once in a higher gear or higher rpm, it is non-existent. I know this truck is tuned for GPM"s, could I just be hearing the engine lug through the exhaust slightly, anyone see this as normal? Thanks in Advance.