J_nova91

hello everyone, new member here from south Texas. I have a question I've been putting off for a while, bought my 2004 Mustang GT 4.6 SOHC from a friend 2 years ago. After half a year owning it, it spit out a spark plug. I know that it's common for these models from 99-04, fixed it with a heli coil kit even though it's temporary. I felt the loss in power and a couple months later the same thing happened. Replaced the coil and spark plug again. Flash forward to now it hasn't acted up or anything. Today it started going below 500 rpms while idling and it shook for a bit then back at 500. I know it's lost pressure so it's time to do something about it before something else happens. Now my question is, what kind of heads do ya'll recommend on installing. I'm not looking to race it at the track or anything like that. My buddy is a mechanic and he's the one that's gonna do the job on it and recommended I don't remachine them so I'm looking to buy new ones or from a junk yard I just don't know how I would go about finding the right ones. I was told by someone that there were three or four different types of heads that came out in the Mustangs during those years. Any help would be appreciated. Thanks. (Sorry for the long post)

Camster

Are you sure that it's another plug issue and not the IAC or something else?