When using a specific collective noun, the proper name for a group of pugs is grumble, as in, 'a grumble of pugs.' Pugs are known for their snorting, nasal vocalizations and involuntary sounds, making this an apt collective noun for this dog breed.
Known for their wrinkly faces and small stature, pugs are a short-snouted breed that has been bred selectively to have certain physical characteristics that lead to some anatomical difficulties. With a shortened respiratory system, including a truncated nasal passage, these dogs are known to have breathing problems. As a result, a grumble of pugs will likely be accompanied by a variety of snorting, grunting, grumbling noises.