2006 2.2 Ecotec. Getting P0300 code(random multiple misfires) only when hot. Went the winter without the problem. Now that its hot and a/c is on i get the misfiring and stalls out. Runs fine when travelling down the highway. Its when slow moving and hot where it acts up. I replaced Coil pack. ECM reprogrammed. Odd thing is i repleaced the ICM on top of coil pack and the engine went misfire crazy. Same thing happened last year when i tried replacing it. Put the original ICM back in and it ran fine until temp rises to around 190 degrees. Any ideas?