msauce18

I have an 05 GTO I bought used. I had a CarFax report run and everything came back clean. I have an engine tick coming from the middle/right side (looking at the engine). You only hear it while idling. I thought maybe it was a valve problem so I took it into the shop. They ran some tests and took a computer graph of the motor. They said to come back in 1500 miles to see if it has gotten worse. I plan on taking it back in this week but so far I think it has gotten a bit worse. They at first thought it was a valve spring sticking but then said it could be the natural motor sound. I also pointed out to them that they car has a rough idle which I thought had something to do with the ticking. Does the car naturally have a mild shake while idling? Does anyone know what the ticking could be?