can i have a twin turbo in my GTI ??

I guess you could do it. There would be a lot of custom work though and it'd be pricey but to each their own. If you want to do it and have the money to drop of course it can be done.

Do you know why you want to "twin turbo" your golf ?

Sure, why?

mate you could have a twin turbo and supercharged engine with 272 cams 500hp shot of nitrous, 40 psi of boost with two external wastegates screaming like banshees............ if you have the money.