It kind of sounds like the clutch is slipping. It could be a coincidence that it happened as he removed the exhaust. But without seeing the bike it's tough to diagnose.
You can check the exhaust valves to see if they are opening and closing by reving the bike in neutral. But if it was the exhaust valve it probably would just fall on it's face and not continue to increase RPM.
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Do you really have to start a thread every time you go on a ride and see a guy with no helmet on?
Does it affect you that much that some random guy 1500 miles away went and paid his own money for a 1000?
Do we really have to fight over who uses the back brake or not?
Do you have to argue over stupid pointless shit on the Internet?