Exhaust sits on the piss when warm?

[A L 3 X]

Strange one people, i've noticed when the cars not been used the exhaust sits nice and central in the cutout of my rear lip, now after using the car the exhaust seems to have moved to the right a little.

Now i've only noticed this since fitting my new decat, however it used to do it with my old powerflow system running a standard cat, so not too sure :/