What is the best way to infill the holes in the extg masonry wall. We were thinking block and grout to match existing to restore the 2HR rating, but would like to confirm the detail. 
Ashley,
If you are looking for a firestop solution to restore your rated wall, we have several options. I am not sure what the size of the opening is, but I will include some common systems for you. Additionally, if you would like to sort through some systems we have, feel free to visit https://www.hilti.com/firestops.
If you want to install concrete blocks and utilize grout, that would fall outside the scope of firestop. As such, it would be best to reach out to the wall manufacturer to ensure that you are maintaining the 2-hr rating.
Thank you,
Jessica Starks
Fire Protection Engineer
