What can cause a fluctuating Idle

(Up and down about 500 rpm in park) and throw Misfire codes ( P0300-P0304) on a 2006 Scion tc? 2006 tc (the car is a manual shift) having idle problems worse if car is in gear at a stop. Idle will go up and dwn in park and shows codes P0300-P0304. Replaced plugs (which had the gap on two plugs closed other two where incorrect gap)cleaned TB, cleaned MAF, replace two vac hoses that had holes in them, checked injectors and still have same problem, car runs a little better but still has problem. Now when I started checking the COPS on the car I had the number 4 pulled out it had spark but did not slow down eng idle as other three had, as a matter of fact it caused the idle to smooth out an stop fluxuating after which when I put it back in the problem returned. So I switched Coils and exact same thing happened. Does any one have an Idea as to problem. Thanks