According to Adam.Y on his observations on some differences regarding AL-31FN engines and Taihang engines:
The AL-31FN engines afterburner takeoff flames looks glamorous blue that's very beautiful to look at, Taihang engine afterburner takeoff flames on the other hand is mainly red and purple somewhat similar to RD-93's color.
The afterburner sounds also different from each other, with Taihang engine seems much deeper, heavier, and steady like bass. And AL-31FN engine sounded more explosive that makes your internal organs tremor.
And J-20 number 2016 with afterburner takeoff also sounded different than previous J-20s. It's got this strong puff sound just like a Taihang equiped J-10B he saw once. Haha.....
And regarding rumors of J-31 in CAC is not true, at least he didn't see it. Don't believe all the internet rumors and think about the information yourself. And lastly he is not very happy about people using his pictures without giving out credits and removing his watermark from the pictures.
The information about AL-31FN and Taihang engines afterburner flame is obviously not new at all, but the reason I did a little translation on his post was because what he said about the 2016 engines difference right after that is kind of interesting. It seems like he was hinting about something.......
seavon make the J-10B pics into a gif.