I have a character that is a level 16 Psion Shaper. He has two iron golems with him at all time (Out of the ten he possesses altogether). He acquired them by first crafting the body himself, he then bought a golem manual and finally had a wizard activate the manual's spell trigger on his pre-made construct. Each iron golem has a challenge rating of 13; does this stack with my ECL? If it does how do you calculate the increase if I have more or less of them at one time?
Since you bought them, each one’s CR is accounted for in the 15,000 gp you spent on the raw materials, the 375 days you spent making the body, the 35,000 gp you spent on the iron golem manual, and the 150 additional days spent bringing it to life. For two, double that. 100,000 gp and three years of work are rather substantial, after all. They have no effect on your ECL.