I've been a long time member here, previous LS owner and a current Continental owner. I just added to my stable an 04 Navigator with 220k miles. The exhaust is very loud, the owner said that the clamp after the cat is bad (I think the new exhaust in whole was bad) it's really noisy because of the drone and vibrated a lot. It has lean codes which I suspect could be the pcv elbow or the EGR valve (got a code for that too) or EGR sensor (common issue too) The rear is all the way up because the air suspension wouldn't work anymore because of bad height level sensors (not sure which one but it's better that's its all the way up instead of down) tires in the front are shot because of this but still drives really good. There are minor issues such as window regulator not working on the front passenger side, door ajar message and check advtrac messages. questions: - is the 03-06 Expedition catback/muffler interchangeable with the Nav ? - if I convert it to coil springs, will the ride be the same or will not be issue since it's old anway? each sensor is $100 and there are four (?) of them. The suncore conversion is $298 which is cheaper than fixing the POS sensors. - if I decided to use suspension parts from an Expedition will that work too? somebody has done the "check suspension" message disable?