No absolutely not it will take off the coating just use a screw driver on the outside edges of the flys to make sue the carbons deposits are gone. at the end of the day no one is going to see dirty sooty flys and after 1000 or so miles they will be black again anyhow. I actually work for Nissan and was thinking of the DET TB`s fitting to the DE engine in my 1.4 sunny using a GTI as a donor car. Please let me know how you get on because im very keen to do this mod myself.
One question? how are you going to get over the MAF problem? If you have open air TB`s you have no way of metering the air. I was thinking of using Emerald M3DK management and using a 1.5 Bar map sensor so I could junk the MAF and have trumpets on the TB`s, to look trick and also sound 8)
Cant wait to see it done. Does the DE heads inlet ports match up to the shape of the DET TB manifold shape?