Vauxhall Antara tuning box

I fitted an "Italian box" tuning box to my first 2ltr antara and it worked a treat. Much better fuel economy and better all round performance. No problems whatsoever. I now have the new 2.2 ltr antara but this has different connecters and so I purchased a new "Italian box", setup for my 2.2 Antara. It was so easy to connect but when I tried to start the car the engine made a frightful racket and shook badly. I stopped at once and fitted my old tuning box to the new connecting cable with the same result. I have put the engine back to normal and it runs perfectly. I am returning this item back to Italy for a refund. They have made no comment on what could have caused this. Anyone out there ever heard of this?