Another Idle Issue?
 

Hey guys this is my first post here, I wanted ask if any of you had experienced this idle issue I have just noticed. (I couldn't find any other threads about it)
So on a cold start I've noticed a knocking sound coming from the engine. It's only happened two or three times but it is definitely noticeable. And it is a manual trans.
So I start the car and it sits at 1700rpm and makes this knocking sound. The tachometer bounces up and down slightly for a little before slowly sinking to 700rpms, and when it bounces up and down I can feel the engine hesitating while i'm in the car.
No difference is made if I engage the clutch or not.
Have any of you guys had this issue/know what to do? Is this just the boxer rumble? Im used to old Honda engines and have never owned a Subaru.
I found a video on youtube that is the same thing my car is doing (my video didnt turn out so great) so I will try and attach it.
Thanks in advance!
[ame="http://www.youtube.com/watch?v=47Vncoc4QdM"]Cold idle issue FR-S - YouTube[/ame]

Popping from the exhaust caused by cold start emissions which was deemed normal engine operation iirc.