The turbo will have a boost guage and you should see under reasonably hard acceleration that the needle will move fairly decently into the white (or postive pressure) area of the guage if all is well with the system. In my case, my 854R's guage goes almost full scale so its fairly easy to see the movement. You may also hear a wee bit of a whistle as well, but not too much as that could be a bad thing.

Now in regard to "seat-of-the-pants", if the turbo is working, you will feel the hp difference (222hp versus 168hp). When I was comparing back to back on a number of 850s I was looking at, the difference was very noticable. It was really awesome when I tried what became my R (247hp) and I had just previously tried out a non-Turbo wagon.

Hope this helps

Bill