OK, may be geting closer to the fix on this. After digging around in the engine bay, I have discovered. the temperature censor the bottom one of the 2 has a very loose connection fiddling. Around pushing the plug on and cleaning has now led to the temperature Gauge not fluctuating when revving. I also unplugged briefly the e g R ( and do not know if there is a connection to this being part of the problem) But when driving down the road, no white smoke. No engine stalling, but it does feel like it's hunting. A tiny bit and with that I have also noticed the temperature Gauge drops. Just a tiny bit like a millimetre. Where the terminal is loose and is not making contact properly. I'm wondering if this is the fault. So I shall replace that temperature sensor a s a p and finish this thread off with success I hope.
I'd actually give the electrical connection to the sensor some more attention, try and clean and tighten it up. Make sure the sensor is connecting properly - it sounds like some attention to the thing actually worked.
If the ECU senses low coolant temperature it will command things differently - more fuel, less EGR.
You might also have a slightly dirty SCV (this causes hunting). It's usually solved by adding a bottle of injector cleaner. My go-to for this was always Liqui Moly Fuel System Treatment, but we were in Tailem Bend for the Supercars round in August and they didn't have any, so we threw a bottle of Nulon injector cleaner in the tank - problem resolved.
Unplugging the EGR valve should end up giving you a Check Engine light. If yours is an older model, you'd get away with putting a blanking plate in (I added one to the EGR valve side of the EGR tube by making a copy of the gasket out of 1mm stainless steel, and didn't make the main hole). This way the engine still thinks it's doing the EGR thing.
