2003 chevy duramax 2500HD 4x4 150K miles, STOCK. i just replaced my glow plugs and fuel filter and it seemed perfect for two days, now its turning over too long again. mainly cold start. whats next? glow plug relay? glow plug controller? help please. any input would help at this point. thanks

 

What's is the temperature when you try to start?

 

ranges from 30-40 degrees F. since i replaced the glow plugs and fuel filter it starts but still turns over longer than normal. and even when warm still turns over a little too long. could it be injecters? or glow plug relay? i primed the fuel filter and messed with the bleeder. im pretty sure i worked all the air out of the lines. thanks