[MG ZS STE]

Just to update on my issue. I decided to go over everything I had removed/disturbed in fitting the thermostat. Removed the TB, there was a lot of oil which had set like tar after the butterfly. I had cleaned some off when I removed it the first time but neglected the hard to reach parts like between the pivot points of the butterfly. So got to these areas with a cotton bud soaked in white spirits, made short work of it. All the edges of the butterfly that make contact with the inner wall of the TB. Both mating surfaces of the TB and inlet manifold, then reassembled tightening the torx head screws in a diagonal order (opposite corners) whilst holding the TB firmly in place the whole process with my free hand. I also checked the operation of the IACV and gave it one last clean with cotton buds and white spirits for good measure before reconnecting everything and firing up. Initially it was a still a little lumpy. That's no improvement at all I thought. Then gave it a blip on the throttle and the revs didn't drop below 700/800 rpm as they were doing before. That is an improvement I thought. It was also idling smooth again. But this was cold and the issue was always hot idle, so gave it a run this morning and it's definitely not doing the stalling and cutting out anymore when approaching a give way situation. The revs are actually holding around 2000prpm for maybe a quarter second when you come off the gas then dropping normally to idle (@770rpm). The throttle cable is set correctly with just the right amount of slack to allow the butterfly to close properly when the throttle is disengaged. But all in all I'm much happier with the way it is now running.