my car is making a DEtonating sound at idle...wtf?

You say your idle is set low, and your friends Camaro does it on startup. Sounds like lack of oil pressure caused, in your case by too low rpm, and in his case, oil drainback.

The oil drainback could be caused by far too loose tolerances in the components (worn) or by a too large capacity oil filter with a cheap anti-drainback valve, or of course, a combination of both.

Try idling it higher, see if it persists. An easy way to check is to just give it a little throttle. If you have an aftermarket oil gauge, it would be even easier.

As for oil filter, I have found that to cure the same conditions as you had (except very very bad) I went back to using a genuine oil filter. It didn't even cost any more, maybe two dollars more. The genuine filter on my car (not a Mustang, not even a Ford) is about 1/3 of the size of your standard aftermarket replacement filter, and has the same amount of filter area, and flow.

As for oil, I'm not really experienced with (relatively) modern motors. How many miles on your engine and what oil are you using now? Do you experience any EXTRA rattling at idle when the oil is hot?

Maybe its cause of them flame throwers lol