If you can measure the thickness of your intercooler, likely the core will be 32mm wide. If that's the case then you'll get a reasonable gain by upgrading to something with a thicker core (Golf R/S3 intercooler).
I've just done the upgrade on a 2011 Tiguan which shares the same intercooler with a number of Passat models - VW Part# is 3C0 145 805 R. To check the model number on your intercooler is a bit of a pain as you'll have to remove the rain tray under your engine and look at the bottom of your intercooler outlet (on the passenger side). There should be a sticker with the part# there (well that's where it was on mine).
I upgraded to an Audi S3/Golf R intercooler Part #: 1K0 145 803 BE which is a direct replacement and bolts up in the same location. It has a thicker core (39mm instead of 32mm) and will provide better flow, more cooling and less pressure drop.
I haven't had my car back on the dyno (yet) though it certainly does feel to be pulling better with less effort.
You're not going to get massive gains from an intercooler. It won't make any more power but it may reduce your losses.
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