Sorry for late reply, dude. You can definitely show to any good garage in Al quoz, Max garage, Technical garage, House of cars etc. Get the computer diagnostic check again i really doubt it all above three things need change at same time, highly unlikely. May be workshop doing more of guess work than falling short of their words if misfiring doesn't get cure with one.
Usually misfiring causes are spark plugs, coils, Air leak / Vaccum leak. Air/vaccum leak can be checked mechanically from outside the engine by listening the hissing or drop few drops of water on and around manifold area. Spark plug and coils are difficult to identify if they faulty, so as a rule of cost change the spark plug first as its lot cheaper than coil and then go for coil. Usually coil fault comes in computer test so you cant wrong on that expense either.