If it's in manual shift mode it is default to shift down to third on its own at a stop. You can manually shift it to first, but only at certain speed/ rpm or completely at a standstill. This is the way the tran software is designed.

When you say your trans "shit itself" what do you mean? Did it quit pulling all together or just the problems you describe?

I also have a 4.6 with the 2-1 downshift bang and it is annoying as hell. The only time I can avoid it totally is to run the A/C compressor which raises the idle a few hundred rpm, or just two foot driving when coming to a stop. I'm planning on upping the idle speed via GT1 to see if this cures the problem. I have a feeling it may just work.

-Ben