I didn't get a chance to adjust the settings and ride before I took it to the shop. New rear spring is on, ride feels much better now.I'll have a close look at my shock, haven't seen any obvious signs or felt it bottom out.
Increased pressure will make the a motorcycle tire, especially performance tires "rounder" and harder, this is why you feel its nimbler, at the same time the harder tire will soak up less imperfections in the road, a more inflated tire can give you more road surface feedback. Overinflated will make you loose grip.
I guess your old bike had a more square profile tire than the Diavel.
0,3 psi shouldn't really be noticeable, typically a tire pressure will increase by 2-3 psi from cold to working temperature, 3-4psi if ridden hard.
I set my pressure in my garage at 20C/68F to 38psi a few weeks ago, outside its just over 10C/50F and the roads are cold, so the tires dont heat up as much now, (spring has been unusually cold this year) in 2-3 weeks I will probably need to let out 2 psi to get down to 38psi as the ambient temperature and roads are much much warmer, then in september I need to bring it up again.
Another thing to notice is that most pressure gauges differ, so either get your own gauge or check pressure at the same place every time.
You can check your pressure at a service station, then cross the road to the next one and have several psi difference.
I have my own gauge and air compressor in my garage.
I do think my old bike was a different shape, more square like you said.
Yeah, I do not know why it felt so much different to me with just 0.3 psi, I mean I know I notice in my car when it goes down 1-2 psi, but 0.3 doesn't seem like I should notice much. Either way I liked the ride much better with just that tiny bump in psi. I have a compressor and gauge, so I am checking with the same gauge every time. Service stations here make it difficult to check pressure or put air in the tires, always try to get you to pay for it, so I've just had my own gauges and compressor for years.