I recently had to get my '97 smogged here in California, so I had to remove my cone intake filter and put the stock one back on (at least they didn't notice the y-pipe ... and I passed!) To be honest, I didn't notice any big difference in performance with the stock setup. I've been wondering if this is because the cone is getting hot air from under the hood, while the stock intake filter is getting nice cold winter air from outside. I'm a bit surprised, since I thought I felt an improvement when I first put on the cone filter nearly 2 years ago.