Yes trader4 i am going to change the thermostat and sure its running colder than normal running temp.Actually i got this suggestion by very knowledgeable fellow at bimmerfest.His dad's car stopped regenerating DPF because of the bad thermostat.As there is a requirement of min engine coolant temp for the DPF regen and his engine was not reaching the proper temp for regen to start and he ended up with clogged DPF.I also read that cooler running engine will damage glow plugs as they activated below 75 deg C.

So did you get any DPF regen issues when your car was running cold due to bad thermostat?