...and drove the Z for the first time today. You can notice some small gains from the low-band. I think its a worthwile mod, for under $200 and I did the installation myself. Do a search for "pulley" and you should find my previous post on my install. Also check out the "Tech" section for an good overview...it really helped with the adjustments you need to move and pull belts of the pulleys. Good luck! Do it!