OK, along with the K&N, the people that are staying with the OEM filter box took the white baffles out AND replaced the tube that draws the air from the fender well with a larger tube and cut it right after it enters the first chamber. Having a longer tube that goes into the first chamber (box) directs the incoming air directly against the far wall of the box causing disturbed air flow. (I didn't do this, only read it in a couple of forums).
You say you have a 2001. Look on the drivers door and see the build date. Top line reading something like 08-00. That's mine and it means it was made in August 2000. If yours was built AFTER July 24th 2000, then our local master mechanic (MX-5) came up with a cure for sluggish shifts between 1st and 2nd gear in the automatic PT. It's called "The shift Burp" cure. You cut a single wire and the shift improves 100%. Read all about it in this thread ......
torque managment, how to fix the 1-2 shift burp - PT Forums - The PT Cruiser Enthusiasts and Owners Resource