Normal acceleration is the way most cars accelerate in traffic.
The higher the load, the earlier the boost kicks in.
There's no real 'treshold' where the boost kicks in.
I just rate it where I start noticing the boost. Butt dyno, if you may.
Below 3k RPM, the FiST doesn't really boost, unless I press the pedal beyond (about 25%) where the Sound Symphoser box starts making more noise (another one of those things where there is no real treshold).
Just in case you didn't know how to google 'ecotec vs ecoboost', I did it for you:
http://bfy.tw/I9JA
First result is the article I mentioned before.
You will have to click it to read it, just in case you forgot to do that before commenting that the search didn't reveal anything..
You can thank me later!