Could just be the type of dyno.
I just got dyno tuned last weekend on a 2wd dyno dynamics machine and I'm at 318.
But I was told that would be about 350(?) on a dynojet.
And of course, we all know that varies by temperature, humidity, etc.
So don't worry about it; just enjoy it.
__________________
Bill
2010 370z; Tour/Sport; 6mt; BlackCherry/Grey;
318 rwhp; 265 lbs rwtq.
To view a list of my mods, click
here; To view a photo journal of the mods, click
here.