I put one on my 00 GS-R about three weeks ago and I think that it has made a big difference. The biggest increase is in the higher RPM range between VTEC engagement and Redline. With the stock air box the car seemed choked off at high RPM's. I changed from stock so the difference was dramatic, my friend has an 01 GS-R and he had an AEM CAI before he also says that he can feel a difference.:thumbup: