Limp mode, code 0299, replace pressure sensor next to turbo, clear codes and drives fine ... for 3-4 months until it happened again. I also have been smelling exhaust fumes around vehicle and had it looked at by a muffler shop where they said its just a diesel and they smell (they had nothing to sell me).
Something is causing these sensors to throw the code and each time replacing the sensor / code clearing fixes the limp mode but it must be something else causing this in the first place. Any ideas?

 

have you checked the impeller play on your turbo? If it's getting worn and loose it can start binding and producing low pressure. Mine failed in this manner (worn bearings) and put me into limp mode, not sure what codes it was throwing though. No idea if your issue could be caused by that, but maybe worth checking the play anyways if it's got a lot of miles on it.