And besides that, my engine temp is very low? -Never above 70 deg. Celsius. -Which makes it hard to heat up the cabin now that outside temps are below the freezing point.
First off, replace the t-stat.
KE uses the coolant temp sensor to activate the cold start valve. I would check for signal to the injector first, then if your stting signal, does it spray.
The surge could be a as simple as a vacum leak or reseting the base fuel mixture. Your area doesn't use that winter blend oxegenated fuel does it? That can cause hard starts and such due to the ethanol content. If so, reset the base mixture and see what it does. (after you check for vaum leaks and cold start signal/spray)