Last winter I blocked the radiator on my 2003 Jetta TDI (EGR removed) with a simple piece of 3 inch thick foam. The car warmed up much quicker and engine held steady at 190°F while driving. Without the foam, the car struggles to maintain temp when ambient temps are below 20°F. I was thinking of doing the same with my 2015 Passat TDI as it is slow to warm up in the winter but am concerned about reducing cooling to the DPF during regens. Thoughts?