我想問這句英文有沒問題呢？

90% of what you're saying isn’t coming out of your mouth.

Wrong! past tense must be used for this sentence.

90% of what you'd said isn't coming out of my mouth.
因為肯定你聽到後才會這樣說.

90% of what you'd said isn't coming out of my mouth.
1) 其中 what you'd said 己是主詞 + subject (you), 故不需加 it 或 that.
2) 字句中己說明 10% of what you'd said were coming out of my mouth. (hidden)
3) 如果你不用 past tense .即表示你是估計而非實情(己發生).
Simply discussion, please correct me if I am wrong. Tks.

這句英文是沒問題的所以不用怕