Looking at rad hoses on my 06. The hose from the bottom of the rad goes to the thermostat housing. The water manifold at the end of the head goes to the top of the radiator. Does that mean the thermostat is on the suction side of the pump? Is it possible that more flow goes through the oil cooler and transmision cooler and less gets to the heater core? Less plumbing going through coolers than going through egr cooler and heater core. Thinking because it's cold in the winter could restrict the cooler flow to increase heater core flow and maybe more heat. ANY body already try this?
Yes, the thermostat is on the suction side of the water pump. No, blocking off coolant flow to the oil cooler will not do what you're thinking it will.
Your theory only works works with positive displacement pumps. Your oil pump is positive displacement...your water pump is not.
Do you know what your coolant temps are now? Is your thermostat and Aux heater working properly?
My 06 Jetta usually runs around 90C at full operating temp. Sometimes I'll hit 92C on bigger hills, and sometimes 88C when driving downhill, or coasting, or sitting in traffic. Between the heater and my seat heat, my car is too damn hot inside. However, it takes about 12 km of driving to hit full temp in the morning after a cold start.
I just installed a Frostheater myself last weekend. I love these things and had one on my previous TDI as well. It doesn't get cold enough here that I actually need the thing, but I love having a warm car on the cold mornings.
Check your thermostat.