Hey, I had a similar issue intermittently for months. Would splutter on 3 and then fire up again and run on 4 for ages.
I ended up not needing to replace the coilpacks, but the bridging / stage connector they plug into. It's screwed onto the back on the air box next to the maf.
Edit sorry sounds like what you were referring to as ICM, when I was ordering the part with my mechanic he called it the stage.