Hello, I saw the OP problem and got thinking. I drive an RX400 h and I find even though I’ve had the car for 6 years it’s pretty impossible to know when the petrol engine comes in unless you are looking at the energy monitor whilst driving. I haven’t driven for 450 new shape but I’m assuming that the technology has progressed from the 400 so you’d expect a smooth transition on par with my RX 400 , but the only time I can tell the engine is coming in is when i blip the throttle to accelerate and then there is a noticeable step or a jerk for want of a better expression, but this is normal... I wonder if the initial jerk is what you are picking up on. Sent from my iPad using Tapatalk