(oops, accidental necro'd, this thread showed up in the "most active" list for some reason)
Looks like you've got some "smoothing" on your low-poly model that's exaggerating the normalmap along what should be a flat surface, you can try just selecthing those faces and just giving them flat smoothing, should fix it. You can weld and smooth again when you're done. And it also looks incorrect around the elevated circular part, the rim shouldn't be 1 colour like that. I don't know why that would be though, not without inspecting both models.