XPS 15 (9530): AHCI driver problem

Hi! I bought an XPS 15 (9530) one year ago with 1 TB HDD + 32 GB SSD mSATA. I replaced recently the HDD with an SSD and installed Windows 8.1 with the Dell Recovery USB.

But the SSD is recognized as connected on a SATA2 port and it's running at half read/write speed. When I uninstall the Intel Rapid Storage drivers and use the standard ones of Microsoft it finally runs full speed and the SATA3 is recognized, but it randomly freezes.

I checked the Windows Event Viewer and I found out it's an issue related to these two events:

- event ID 129 storahci in correspondence of the freezes (of 20 seconds)

-event ID 153 disk ones every 20 seconds continually

Does anyone has an idea about how to solve this issue? :( Either solve these two events or fix the SATA recognition port with the Intel Rapid Storage drivers and performance issue.

Thank you! :)