What is the meaning of "Taflu [Alai Sheker]"?
Rashi: [Sheker] ganged up on me. The same applies to "va'Titpol Al Avoni" (Iyov 14:17). Radak - they said that my inside in unlike my outside (I pretend to be more virtuous than I truly am).
Malbim: There are two classes of intentional sinners who argue with Torah and Mitzvos. The first deny Torah and Mitzvos via lies that they fabricate; refer to 119:69:2:2.
Why does it say "b'Chol Lev Etzor Pikudecha"?
Radak: You know that [my inside in unlike my outside] - I guard Your commands with all my heart!
Malbim: Corresponding to those who make up lies to deny Torah and Mitzvos, I guard Pikudecha with all my heart. They commemorate Hashem's miracles in days of old - they testify Emes against Sheker of the Zedim.
