I decided to try to get out of leecher.
I had a MPQ in my data while I was patching to 2.3, after it had patched it was still in there, I logged into WoW and had forgotten about it. I went into my paladin and it was still doing the effects.
If I took the MPQ out of the folder, WoW wouldnt start.
So I think this is a way to get MPQ's to work without a MEF