Thanks for your response,speaking of air filters i use K&N not to help performance but it's cheaper that and less of a hassel then replacing them every 2-3 months,anyway there is alot of soot build up after about 60,000 miles i know the build up is good per K&N however i don't know if they consider the fact that it's a turbo diesel [7.3] anyway was wondering what you thought.I have one in my car (gas engine) and haven't cleaned or changed it for 40,000 miles it has the bugs and leaves and dirt but not the heavy soot.