This is not a performance improvement, its an arquitectural change that has to be accounted for when using Unicorn. Unicorn is NOT for slow requests, as their own documentation explains. (http://unicorn.bogomips.org/)
On Kaya.gs to handle 3rd party requests I built a queue, which has the advantages of being able to be light on environment and have a small footprint.
The title is enticing as well, as this has nothing to do with Heroku.