http://www.myturbodiesel.com/1000q_how_to/multi/IQadjusthammermod.htm If you've never checked the fuel injection quantity on your 1996-2003 TDI it's possible it's off. Included are VCDS menu screenshots and how to do the hammer mod. Fuel injection quantity (IQ) adjusts power, smoke, and economy. It can be misadjusted from the factory or it can change after a mod to your car. The middle section of the injection pump adjusts IQ using an electronic arm. However, the electronic arm has mechanical limits. The hammer mod changes the mechanical range of motion on the arm.