00 Acxord LX idle issues
 

I have a 00 Accord LX with the 2.3L 4cyl VTEC. Now I bought it used, & have only done regular maintenance, (oil change, filters, etc.) I have never owned a Honda before, but I learned quickly that the previous owner was trying to 'performance tune' this car. So far I see a K&N air intake filter, AM headers, & exhaust, and several stock under the hood items were removed while installing the aforementioned parts. It leaks oil. I recently put a new water pump water pump inlet pipe on it, due to a HUGE water leak. Here's my issue: When I engage the clutch, the car's idle speed drops as low as 200 RPM & sometimes it will shut off. It seems to idle really low anyway (750 RPM) any suggestions on where to start checking for a problem to solve?