I think you mean 1 gram acetyl carnitine?

Try this. Cut back to 500mg of acetyl carnitine daily.
And cut back to one fish oil daily. (some people get loose on fish oil-- if they do not absorb it well)

If you still have loose stools, it might be the magnesium type you are using. If you are mismeasuring it? Citrate form is the type used in laxatives. So switching to a delayed release form tablet may be easier on you. People vary in the response to magnesium. I like the Mag64 myself.
I am very sensitive to mag myself. So I use almonds as a snack daily to get mine usually. I only take supplements when I have stresses like working out, or more exercise than usual.