The air suspension is the main issue with the P38, but also watch out for porous blocks on the 4.6l (the 4.2 is less prone to the problem). Also be warned of the problems caused by faulty BECMs (body electrical control modules, which operate all the lights, doors, windows and wipers, amongst other things - the switches don't directly control anything but run through this ECU). New BECMs are not available and rebuilt ones are relatively expensive. the problems are normally dry joints, so you may be able to get a faulty unit repaired, but a spare might be advisable while you can find one. The air suspension parts are very expensive and any leaks tend to wear the compressor out quickly. Many people convert to more reliable coil springs with kits such as Atlantic British, but you then lose the increased ground clearance off road and the lowered entry and motorway cruising heights. It all depends on how much you want to spend and how reliable you need the vehicle to be, such as for overlanding.