Got about 8,000K on my 2006 Dakota V8 4.7L SLT and can't help but noticing the dirty black tail pipe all ready. My gas Milage is nothing to brag about 17.4 L / 100k 13.4 miles /gallon. What's the deal with that, I wonder how bad the build up is in the motor??? it looks like the Chokes on a bit or something. Anyone got any ideas?