Hi Ian, I had a 2016 Aero 8 and now have a Aero Plus 8 and both have the tendency you describe but only when cold. The plus 8 tends to have what I liken to a cough after initial start with around 800 RPM then after the cough the revs drop to 500 / 600. The Aero took longer and usually the car was underway and did as you described which was disconcerting initially but had the car for 4 years with no ill affect. As they say "They all do that sir". Hope this helps. Ron.
