You purchased the wrong hop up unit. Yes they are both for M4 series, however there is a huge difference between a one piece hop up unit and a two piece (different manufactures use different hop up designs). The one piece hop up chamber you purchased is made for a Classic Army or G&G (and others) body style of M4.
Like AngelusNex said, our tech won't do anything like modifying without your acknowledgement. Once a part is modified, it cannot go back to the way it was, and if modified incorrectly that part would be absolutely useless. Modifying is more so a desperate last attempt if nothing off the shelf is available. Most people would just end up buying the proper part to have it installed.
As for your sorbo pad, our tech has tried numerous attempts with it. The installation part wasn't hard, however the sorbo added just too much of a spacing to your piston causing your gun not to function properly. In the end the tech decided that removing it was the only logical solution. Additional time spent on it would only cost you more as you are paying him by the hour. In fact I recall him billing you less then what he actually spent time on the gun as he didn't feel you should have been billed for him trying time and time again to figure out why the sorbo wouldn't work.