I agree with those below: Please get him evaluated as soon as possible and see what kind of professional intervention he may need -- occupational therapy, behavioral therapy, etc. This may or may not be sensory, it may or may not be something else, but you have made a real effort for over a year and it's not changing, so it's time to turn to the professionals.
Four-year-olds do get easily frustrated all the time, and I generally don't embrace the idea that all kids' behavioral issues mean a diagnosable condition, but if his anger seems really too intense for a young child it's worth getting him checked to see if this is normal four-year-old need for control, or something more.
Remember one key thing if your son does start counseling: Therapy or counseling are for you and your spouse as much as for your son. You need to talk in detail to the doctors and ask them to give you specific ideas on how to explain things to him; how to react to him when HE is over-reacting; how to work on his environment; how to spot the things that will trigger his anger (anger is often a sign a child is actually scared, more than angry, and that's something a therapist can explore). Until you get him (and you) to a therapist, meanwhile, sit down and think hard about when and where he seems to get most angry, and try to reduce or eliminate whatever sets him off. But don't go it all alone; get him evaluated.
Is he in preschool? If so, I would talk with the teachers (without him present) and get details of how he acts and reacts to things there. The teachers may be a very good gauge of whether his anger seems like normal frustration for a young child, or whether they think his anger is beyond what they usually see in kids this age. That's good information to have if you go to a doctor.