When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So you're posting in the air cooled 911 specific forum, and you may get a more accurate answer if you re post in a cayman specific area. That said; It looks like a resonance flap, that would be used for changing the volume of the intake manifold for different parts of the RPM range. The 964 engine has something very similar. The change in intake volume changes the resonance created within the manifold that is used to increase cylinder filling. If you lock it in one position you will be very sad with the result. You will either lose somewhere near 10% torque in the low end, or take a big whack off the top end power. If you do some searches you can find dyno sheets where 964 owners or shops have locked them out to show the measured effects.