1) Do a toy time out... or one Mom I know actually put most of her son's toys in a box, on a shelf.
He had to "earn" it back, one by one.
*Do a "Redo". ie: when he talks back... say to him "Redo." Meaning, he gets a chance to re-do what he just said... many times a kid is impulsive with their mouth/actions. But don't think about it first. So, offer a chance to "Re-do" it. Tell him it is a chance to correct HIMself. Before getting the actual consequence, if need be. Many times, just re-doing something for a kid, can help.. because then it makes them "REFLECT" on what they just did "wrong."
2) Tell him talking back is not acceptable. Teach him HE is a PART of the FAMILY.... and being a "Team." Kids Need to learn how they are a part of something bigger than themselves. It is about caring and helping each other.
3) Give him 3 warnings... if he does not listen to you tell him "Mommy will not listen to you....until you can cooperate and talk nicely... AND you may not talk anymore." then go and sit down, open a magazine, and do NOT talk to him. If he talks to you repeat "You cannot talk until you show me you can respect Mommy and talk nicely..."
4) Get 2 pieces of paper. Draw a happy-face on one of them, and a sad-face on the other. Each time he talks back... write a tally mark on it. Don't say anything... just do it. Post it up somewhere where it will be seen, somewhere central. He will be curious about it. If he asks just answer calmly (not in a 'lecturing' voice) that anytime he is nice and cooperative, he gets a tally mark on the "smiley" face. If he does not cooperate or is sassy or talks back etc., he gets a tally mark on the "sad" face. DO NOT explain that he gets a treat or something for smiley faces. Otherwise they only work for the treat... NOT the "lesson" it teaches. AND... you can then VISUALLY show, your Husband, Daddy... how many tally marks he got each day for either smiley/sad face. BUT... when he is proud and you are proud of his behavior/accomplishment, PRAISE him.
5) Use an egg-timer ... to designate how long he must stay in time-out... or to illustrate how many warnings he gets.....
6) A kid's life, is basically one in which they are always told what to do and what not to do. Not real fun. Does your boy get a chance to just be silly and do nothing and just hang out? Kids/boys need that too... to get their pent up whatever out. Try talking with him. Teach him about emotions... to say when he is frustrated/sad/happy/disappointed/worried/stressed etc. Just gabbing with a kid, really helps too... and it is a bonding thing. It may make him feel he is "accepted"... or that he can tell you things. My daughter, really bonds with me that way, and then her behavior gets more positive.
7) Some kids act like that to other people when they don't feel THEY are being respected in return. Its a sort of passive-aggressive thing.
8) If he is moving up and down the stairs during time-out... I don't see that being a problem. The main thing is that he is ON the stairs. Not how he does it.
9) Some kids, talk back or get passive aggressive when they feel they have NO lee-way in their behavior or mistakes. Its frustrating. So they just get irked if they are on a real short leash so to speak. (not saying this is you... just ideas).
10) He is 4 years old... have him do chores, if he does not yet. It makes the child a PART of the bigger picture, a part of the family. My daughter gets real proud of "helping"... she even volunteered to wash the window screens once! BUT... the point is NOT that the child perform it "perfectly"... the LESSON in it is just that they try their best and do it... and that it can make Mommy happy and the house or their stuff look nice. Just 1-2 chores... nothing hard. Age appropriate. It helps some kids just to feel "proud" and productive.
Whatever you do, it has to be consistent.
Just some ideas.
All the best,
Susan