Question on Boxster Common Engine Failures

Hi I have a Cayman 2.7 triptronic S, on an 07 plate, it's done 22k miles. Driving today on a the motorway I had put my foot down a few times with no issues. Further in our trip after just driving at 60-70 I put my foot down to pass some traffic. When the car reached 70mph plus there was a very loud noise which sounded like something wrapped under car flapping, it was seemed to be coming from the drivers side rear wheel area. I immediately slowed and noise stopped, I took the next exit pulled over to check the car. I thought my tyre had blown when I checked the car nothing seemed wrong, there was nothing hanging off and nothing oblivious wrong. I then drove under 60mph to meet my parents and no noise, I took my friend in car and put my foot down to see if noise happened again, and sure enough once it was over 70 the flapping started again.
I was just wandering if anyone could explain what might be wrong with my car?

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Common Boxster Engine Problems and Failures - 986 / 987

[Nick at Pelican Parts]

Check the plastic trim panels or engine splash shields. Something may be loose.

- Nick