As stated bt the guys above, sort your induction and your exhaust. An engine is like a lung , the easier (to a point!) it can breathe in (Cold) air and breathe out spent gases , the better it performs. The "Chip Tuning" merely adjusts the computer setings to make the best use of the improved breathing. TDI have free flow filters for your car , or indeed a Complete induction kit , as for exhausts , they do a De-catted manifold , and complete systems . Also Mat C (Supracharged IS340) is getting Manifolds and systems made too.
Or you could just go buy a Supercharger........
Hope that helps some buddy.