100% on the Pericope Adultury.

• It says Jesus wrote on the ground with his finger in the Second Temple... the STONE ground. John (or the author of John) would have lived and visited the area of the 2nd temple and known it was stone, but the forger who wrote the Pericope Alduterae 500 years later obviously had never been.
• It uses word choice that isn't present anywhere else in John, or the books with the same author.
• If you read the end of John 7 and skip over the to John 8:12, you notice that it flows much more sensibly instead of having some bizarre backtracking for no reason.

Once you know to look, it's an obvious forgery.