I have seen these around for various setups, and I was wondering had anyone used one here before? IE it would work like the piston in an external wastegate air to the top and bottom. I could see its benefits..

http://www.amazon.com/s?ie=UTF8&rh=n...ctuator&page=1

 

I don't think they have a linear seal in them at all so there is no seal on the lower chamber area. This would likely kill the whole point of the setup. Tial's aren't 100% sealed either on the lower side, but they do have tight tolerances on the wastegate shaft that creates only a small bleed.

I saw one on Full-Race's website a while back that looked like it may have had a linear seal on it. Check with them and see what they have to say about it. It looked just like one that comes off ebay from Japan for around $150 but they might have been modifying them for use with a seal.