Although rule changes were supposed to halt such exhaust developments, Lowe has admitted that all major teams are working on the area.
"To the extent [Red Bull's progress] has been down to exhausts, I'd consider that to be fair game," he said.
"All leading teams are working in that area. I don't have a problem with it."
McLaren are 101 points behind Red Bull in third place in this year's constructors' championship.