Interesting - Fabspeed will regale you with 458s making 450 rwhp stock so that their tune + headers + cat makes another 70 hp at certain rpms:
http://www.ferrarichat.com/forum/458-italia/352748-fabspeed-458-performance-package.html
what to believe?
We dyno'ed the 458 in 5th gear, which has a ratio of 1.03. I can provide graphs to show this, or you can watch the video and see clearly the gear indicator on the dash shows a 5.
In reality you can dyno a car in any gear you want, so long as when you are making comparisons, you maintain the same dyno procedure. Dyno'ing in 1st or 2nd gear will not provide good data however.
I have heard some guys make claims about why you should dyno in X gear because it is more efficient ect. ect.......in reality they are just looking for a higher number or higher graph to make themselves feel better. On the 458 as discussed here dyno'ing in 3rd or 4th will give you more torque multiplication to the wheels and thus more area under the dyno curve. Fabspeed as a company in general is not about peak numbers - we care about deltas, as do most of our customers.
Some of the cars we do are dyno'ed in 4th gear to keep dyno drum speeds down, that is the only reason.