I've got an AW M3 with clear bra (Ventureshield) as well. I've been using Plexus on it for just about a year, and it hasn't yellowed (i'm going to continue using it).
That being said, a lot of installers are moving away from Plexus and recommend using just regular sealant on it, or specially designed PPF cleaner. I believe Premier sells a special line of PPF protectants.
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