I'm not sure what your friend "shaderman" is talking about.. tangents and normals are always float3 (they are direction vectors)..what would the fourth component be? Usually only position vectors are float4.

As far as the mirrored problem goes, this is common problem...you may want to adjust your mesh a bit to make sure that the vertices are welded at the seams, and try breaking the model and rewelding.

Also try searching the web for info on mirrored normal maps...there can be a number of issues causing this.

If this doesn't work, there may actually be something wrong with the tangents that A6 calculates--I'm pretty sure there is as I get better results when I calculate them myself using a dll. However I thought this was fixed in the latest versions..