2006 2.2 Ecotec. Getting P0300 code(random multiple misfires).Runs fine when travelling down the highway. Its when slow moving where it acts up. I replaced Coil pack (NGK) and spark plugs (AC Delco Stock). Odd thing is i repleaced the ICM on top of coil pack and the engine went misfire crazy light flashed and everything. Put the original ICM (Stock part) back in and it runs fine but still stalls occasionally . Any ideas?