General Maintenance & Repairs - Cam Positioning Sensor??

Well I put longtubes in not to long ago with a ORY. Expecting the damn thing to run rich which it does i was not expecting this. After install we plugged it into a diablo tuner and it said ses light was due to no cats and this sensor. The car rarely starts on first try. It has never done this before the headers. So it either went during install since the car has 186,xxx miles or its slightly unplug witch my shop teacher thinks. Im bringing it in to school on tuesday so, I need to know what you guys think and where exactly is it? I was told back of the motor but how hard to find and reach?


Thanks

Chris