I have swapped out the thermostat from my 540i to see if that makes a difference. I need to finish bleeding the system out and see how it does. I need another cold morning to be 100% sure. My thermostat form the 740i appeared normal, but I haven't ohmed it out to see if it really failed. When I started the car last night there was no CEL or misfires so confidence is high.
1999 540i/6 MSport- Halos, Facelift Tails, Debadge, Maint Done
2010 Mini Cooper S- Bone stock TURBO
2000 323ci Beater, debadge