For the TDI enhancing the air getting into the motor always helps. Be it by K&N filter,(don't go with the cone, the drop in is preferable) ram air, (loosing the restrictive airhorn on the stock airbox and running lines to the front of the vehicle. And also loosing the screen that is in the air inlet, on the NB's loose the lower airbox. This is all very cheap to do. More expensive would be a better exhaust like the TT cat back system. It will really take advantage of the chip.