Actually my wife wnated them so we could open them when going in to car shows and cruise in. they have been opened and closed a lot in the 5 years they have been on the car. Work just as good now as the day installed.
I would not buy the butterfly design, they are cheaper, but the Dougs seal like they are not there.
Have them on my Dart, Great for getting attention when pulling into cruise ins or
shows. Do not see them helping overall performance. Im running the QTP's no problems in 2 yrs.