I thought Delo made a 10w30 that was diesel rated?
I did check those bolts, and found the bolts holding the bracket to the block loose. Actually, one was loose, the other missing. I tightened the one and the surging is gone. I also now notice a change in note when I pull the start knob that wasn't there before. I do have to wonder, does this being loose really change the timing that much? I can't imagine it's good for the timing belt, but in my experience it takes 3-5 degrees of timing to make these sorts of events happen.