2012 Speedmaster Popping Out The Exhaust

I just bought a 2012 Speedmaster with only 1089 miles on it and at Idle and when deaccelerating it pops very loudly out the exhaust on the left side of the engine only I changed out both plugs yesterday and the left was much darker brown than the other which looked very normal . I think I may have a bad injector but the bike runs good out on the road , It sound like it is starving for fuel at Idle , I am kinda new to fuel injected Triumphs and looking for help.

 

Thanks I am going to eliminate the SAI and see if that solves the problem

 

Already watched it thanks and that is what’s wrong with my bike