Misfire, tough idle - fuel injector issue?

[StartX5]

4 months ago, my 2008 3.0si suddenly engine shaking, tough idling right after i started. Engine fault display on the dash board. and it was misfire number 6.
With 90,000+ miles, i replaced all 6 new spark plugs and ignition coil. and replace air filter. The car running perfect until last 2 weeks ago:
Sometimes after i stopped at stop sign/red light, It's shaking and lost power and engine fault appears on the dash board again. And this time misfire number 4!

Sometimes it shaking and misfire, sometimes it went off and back to normal.
I have mix 2 bottles of fuel injector cleaner for each 3/4 tank last 10 days. and the misfire issue is still on and off sometimes.

I am thinking to replace 6 fuel injectors this time.

Any ideas?