UCF1 Smog Help

I went to go get my LS smogged today, and two places couldn't figure out where to put the clip that detects the car's RPM, IDK much about smog so I was wondering if someoen could help me out, I know I pass smog, because I did last year, I just can't remember where they put the clip, I'm in vegas BTW

The OBD port? There are 2 for every car (one under the hood) the second under neath your knee. (in the plastic)

^^^no not that.
 
its a clip with a wire that goes on a wire in the engine bay to detect the RPM's

I just ended up taking off one of the panels to expose the spark plug wires then took it back to get it smogged, I know there is a way you don't have to but I didn't feel like bothering.