In a Dec 2018 article in Car and Driver they say the CX5 turbo top speed is electronically limited at 130 mph. I believe the CX9 has the same engine and transmission so it could be the same. If you had pushed yours just a little harder you might have found the answer.
I was under the impression vehicles had to be limited to no faster then the factory tire speed rating. If Im not mistaken the cx-9 factory tires are HR speed rated which would be 130mph.