I purchased an extended warranty for my 2005 Yukon XL in 2005 when I purchased my truck. Last week my truck started making a noise so I took it into the dealer. They said it sounded like an engine problem, so will call the warranty company to get authorization. Well you can believe my shock when they called me back to tell me that the insurance would not cover because I had modified the engine. Total shock as the only thing I did was change the air filter to a K & N filter which is a better filter than the stock one it comes with. They... read full review »