Driving in Italy is a bit like eating watermelon... You know the rules of how to eat, and so does everyone else, and yet somehow it still ends up all down your front.
Anyway let me put those rumours to rest for you.
You should ALWAYS drive within the law! If the light is red, stop. If the limit is 100, stay at 100 or less. Just because Italians don't follow the rules doesn't mean you should, they are habitually bad drivers and because of that it works, however throw a foreigner in who doesn't know what to expect and this could lead to chaos.
You will make no friends on the road in italy so don't try to. Drive sensibly and you will be fine and have more time to react to the stupidity around you.
Also another rule, when a driver is flashing his lights at you this does NOT mean please take the right of way like in most countries, this actually means 'I'm coming through, get out of my way'.
Generally speaking the further south you go the less discipline there is in the driving and the less likely you will get in trouble for being over the speed limit.
But as before my advice would be ignore the crazies and be on your best behaviour when driving. If you have an accident you are the foreigner and for this fact alone the fault will be yours!
Happy travels
Kenzo