so get someone to buy one for you and ship to you with declared value of $3.50

German customs tends to start smelling a rat when you ship something worth hundreds of dollars declared as a few bucks. Not sure about Italian customs, but they may think along similar lines since Italy is again on a mission to collect more taxes etc...

Extremepsi is only a few minutes from my house. If you want to order an IC there, I could pick it up and ship it over; declared at a somewhat more realistic value.
EXTREME PSI : Your #1 Source for In Stock Performance Parts

The Garrett cores are also highly efficient and their prices are great. Look into PN 703518-6018 for example.
You can buy these for <200 € in Germany, only need some endtanks and someone with alloy welding skills.
2" piping should be enough, wouldn't hurt to go 2.25", but people are pushing 700hp through 2,5" piping. It isn't ideal, but it works