Have you tried Kegety's antilag?
www.kegetys.fi/d3d-antilag-v1-01
I also use IObit gamebooster.
I also get lag when I use high time compression on the map,mostly near land but I can live with that.
It's strange that your's is a problem that has developed recently. It sounds like it is a factor to do with the computer rather than the game and/or mods. But I'm no computer genius