(preface: Im in Australia so air temp is not cold in the morning lol)
Just purchased a 2005 V6 2.1 about 2months ago, it makes that exact popping/spluttering noise when it idles on first start of the day. After the engine revs and then settles (out of park) the noise will stop and the car drives like a dream. The noise will not occur during idle again during the day. Really hoping that by 2021 somebody can give me a "most probable solution" that they had fix their car! 😁