The deflector will affect the engine. The backpressure is greater than with the undeflected muffler, which makes the engine run richer than usual, thus requiring you to lean out the mixture to run correctly. The loss of the deflector will reduce the backpressure & instantly lean the engine out. If you had it a hair on the lean side to start with, it could kill the engine in flight, particularly if you were at full throttle when the deflector came off.