I started out with the Raceone A duct and didn't like the fit (there wasn't a straight edge anywhere on the duct) I bought an other replica from somewhere else and was not at all impressed with its quality either (it didn't have the lower tab). I finally came accross a genuine Turbo A Duct and jumped on it. I've heard the Abflug is by far the best replica (maybe Shaeff would sell you his). But if not then fiberglass in some studs and be prepared for some serious sanding to get the Raceone to fit well.
If you look on the inside of the bumper cover there are markings that show where to cut/drill for the OEM duct. I didn't notice these until it was too late, so I ended up fabbing up some aluminum bar brackets.
The duct sits a tiny bit high an slightly crooked
Genuine Toyota:
You can see the studs, and could bond them in in the same general area, the replica is stiffer and won't need as many though.
cut out the bumper with a cut-off wheel and a big grinder (36 grit):
And bolted it back on the bumper cover:
I pulled it back off and put a coat of paint on it to keep the rust in check.
Pic of the brackets I used to bolt the duct to the bumper skin:
It took close to 2 hrs. to cut and grind the bumper
