Wow! I am glad my family is not the only ones dealing with a crazy four year old. I had always heard that the twos and threes were the times that were difficult. No one warned me about the fours. My husband and I are going through the same thing as you. I find myself wishing for the terrible twos again or for kindergarten to start. In fact, we started seeing a family counselor just to get new ideas as to how to address his behavioral issues. Through this counselor we learned a couple of things that have seemed to help. First of all, you need to take a few days and assess your own behavior in response to your son's behavior. Keep track of how many times you are correcting your child and how many times you are complementing your child. The ratio to strive for is 5 complements to every one correction. Secondly, assess whether your responses to his behavior reinforce/reward his behavior or discourage his behavior. Positive reinforcement is a reward for his behavior, whether it is good or bad. Is he acting up to get attention? Children who do not feel they are getting enough attention will try to get any attention whether or not it is good attention. Then again, complements, treats, stickers, whatever can also be positive reinforcement for good behavior. Conversely, negative reinforcement is something that discourages the behavior. This can be a punishment for a bad behavior. But then again, ignoring the good behavior (or not recognizing it) can turn out to be a negative reinforcement because eventually the child can turn to bad behavior to get the attention from the parents. Once kids learn they can get what they want by acting a certain way, the pattern is set. In assessing myself in this manner, I was able to determine that some of my responses were encouraging my son's behavior and I was becoming so frustrated that I did not recognize when he was acting in a way that I wanted. Last of all, when your son is acting up, respond only if his behavior could cause harm to self, others, or property. Otherwise do not react to his behavior but then thank him when he stops. An example of this is to be if he is making some kind of repetetive, annoying noise. You should ignore this as it will not hurt himself, others, or property. When he stops making the noise thank him for stopping the noise.
I do not know if any of the above will help you, as my husband and I are learning to utilize the above recommendations. The responses do not feel natural yet and are against my instincts to yell, do time outs, and pull my own hair out by the roots. That being said, when we utilize the above recommendations, our home is starting to become a more peaceful, pleasant place to be. Good luck!