Usually if the converters are plugged up it's going to affect the power on the engine. When you try to accelerate there usually won't be any power. A quick test to check the converters is to remove the O2 sensors BEFORE the converters and drive the truck. If there is more power with the sensors out, it's possible the converters are plugged. Most of the time it's the raw fuel going into the converters from the misfire that causes them to glow red.
As for the misfire, check for vacuum leaks around cylinder #3 and try swapping the fuel injector. If there isn't any change then do a compression check on cylinder #3