I have a 2005 Z71 Colorado Crew Cab with 148,000 miles on it. I have taken good care of the care with all tune ups on time and I run Mobile 1 oil only. The gas mileage has taken a nose dive and the engine is running rough. Also my engine light and ABS light is on. Before I take it to the dealer for service has anyone had the same problems? I always take it to a dealer for service but I want to get an idea of what I may be getting in to so I don't get my wallet cleaned out. Its a great truck and I want to keep it until it no longer runs. This is my 3rd chevy that I have put many miles on and it seems like these problems always happen at high miles. I have been looking at different forums online and I can do a few things first like change filters and plugs and clean the mass airflow sensor. I'm going to do that and see what happens. Next will be the auto parts store for a code scan and see what comes up if there is no change. I called GM and spoke to a customer service rep named Gina. She told me about a known issue with the exhaust valves and GM issued a dealer bulletin about it. GM extended the warranty on the parts to 100,000 miles. I never received this information at home. It would have been nice to know this 48,000 miles ago. I was told to take the truck to the dealer and have a diagnostic test performed to see if this is the problem. She then told me if there is a problem with the head GM and the dealer may be able to work out something to help me. If GM knows there is a problem with a component of their vehicle it should be taken care of as a recall. I made this statement to rep and I was told that she understood what I was saying but thats the best they can do. So now the adventure begins and I'll keep posting my progress.