I noticed something interesting on the Grob 2500 air filter housings and am unsure if it is correct. On our 109B there is a hole in each of the air filter housings that appears to allow outside air to enter without passing through the filter. The hole is located on the carburetor side of the housing and the existing air filters only block about one half of the hole. Either something should be there but is missing or the air filter gaskets are supposed to cover the holes completely. It is possible that the prior owner installed the wrong size filters and the hole should be covered. Please let me know if this is something you have seen on your aircraft and know what these holes are for. (I attached a picture and hope it helps)
Also, I am not having any luck with finding a good part number for replacement air filters. Any help with part number(s) and a source is appreciated.
Thanks - Robert