Funny you should ask. I'm Ken's webmaster... we are currently working on the web site (He's too busy designing and producing his parts to finish the site content

).
I haven't really noticed any drop in temp.
His web site URL is
http://www.kdgarage.net. (Only a placeholder there now).
Email him for more details, or come on out to the MkI meet next month (link below). Ken will be there and you can see his products installed on his 87SC. He also has an alternative to the scoop... Its more of a "sculptured" vent that follows the natural airflow of the MkI. I strongly suggest just coming to the meet and talk to Ken. He loves to talk shop about our cars and his products.
http://www.mr2oc.com/showthread.php?s=&threadid=49651
EDIT: woops... just saw on the other thread you're NorCal. Ken and I drove up for the Beach meet you guys had not too long ago. We will probably be back up there again in the future. In the meantime, just email Ken and he'll answer all of your questions.