First, keep time outs to one minuit of time out for every year of the childs age. (A 2 year old gets a 2 min time out). Second... Ignor him. He throws the tantrums and you put everything into stopping them... just walk away. If there is no one to "entertain" with the tantrum it will stop. Obvously, be within ear shot so you know that your child is safe and not crying out of pain or fear.
When my son calms down he comes to me for a hug and we talk about the situation. You will be surprised how fast a tantrum stops when it seems like no one is listening! Good luck!