tam ‧ per /ˈtæmpə $ -ər/ BrE AmE verb
[ Date: 1500-1600 ; Origin: Probably from temper ]
tamper with something phrasal verb
to touch something or make changes to it without permission, especially in order to deliberately damage it:
He noticed that the instruments had been tampered with.
I don’t see the point in tampering with a system that’s worked fine so far.