do not buy professional products. they are made super cheap. bad castings, made in china...need I say more? google it and you will see
edit: it seems lately that they have quite a few 4.6L guys using some of their products. I remember reading a few years back how bad their intakes, TB's etc were on their 5.0 stuff.
I have a polished professional products TB, can't beat the price of them although it took a little tweaking to get it to fit right. Still rather have this one than a BBK that whistles and looks like balls after a few years lol.