Car started exhibiting power loss, which we later learned was "limp mode". After research we realized many other Mazda owners had a similar problem with the diesel engine in Mazda 6, Mazda 3 and CX5s which is caused by the Diesel Particulate Filter (DPF) clogging. Had a scary experience on the freeway where a truck was behind us and the car suddenly went into limp mode, nearly got cleaned up. We took the car to our local Mazda dealer 4 times until eventually they said they though the fault was that the MAF sensor needed replacing at a cost of $1000. We had the MAF replaced and the car lost power 10 minutes after we drove it out of the driveway. We went back and demanded a refund as the dealer gave a guarantee that this would fix the problem, despite us urging them to look closer at the DPF system as other Mazda owners were experiencing similar problems. They completely disregarded our pleas, despite the DPF engine light coming on multiple times. Dealer ended up refunding part and said that we should contact Mazda head office about the labor as they only followed their manual guidelines. Contacted Mazda, but no response. We knew the DPF was likely to fail so we arranged to have a mechanic delete the DPF system. Before we had the opportunity to get to the mechanic DPF completely failed on the freeway causing the engine light to come on. A DPF regen was attempted but failed, the DPF system was stuffed. Mazda had quoted $8000 to replace the system. We elected to have the DPF deleted instead at a cost of $2000 but the car is now blowing black smoke and still has the power loss issue. It is clear that the engine problem has lead to a build up of soot in the DPF causing it to fail. We are over it and are trying to get rid of the car at only a fraction of it's purchase cost ($6000).