///They are powerful chewers and will resort to chewing anything they can find around the home if left alone for long periods of time. This is simply because Staffies quickly become bored or stressed when left to their own devices.///
From
http://www.pets4homes.co.uk/pets4homes/home.nsf/breedinfo/staffordshirebullterrier
I was not being unpleasant with my reply yesterday, but if you do literally just sit and watch him he may be bored because you're not interacting with him which is what you need to do.
Our own Staffie is a terrible pest at times, but a quick word or a fuss keeps him happy for a while, they are a very tactile breed.