I've had this same problem, I went over this with Gary Herrig and we tried cleaning the ground contacts near the battery. This sounds like the problem from what you guys described. I even put a heatshield around the starter months back, but looks like this is the way to go.
Started getting old getting caught at the gas station and not being able to start the car and having to push it out of the way. I finally ate up all the battery had and then had to get my gf to drive down and give me a jump.
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