I'm assuming that you already patched your DSDT with the DTGP method. If you don't know how to do that, the InsanelyMac community is filled with information about DSDT patching. Proceed at your own risk.
1. DSDT (Differentiated System Description Table)
*GFX0 Section in DSDT
I followed this topic to hack DSDT, but my dsdt have already existed _DSM method, and I don't know how to add more code in DSM method. This is my dsdt, please help me (I want to rid of Nati.kext )