Complex sentence: The M-107P engine proved unreliable and in late 1942 it was changed to a M-107A, while the 37 mm gun was deleted in exchange for another 20 mm gun mounted on the side of the fuselage.
Split into simpler sentences: The M-107P engine proved unreliable and was changed to a M-107A in late 1942. The 37 mm gun was deleted in exchange for another 20 mm gun mounted on the side of the fuselage.