Agree with Lesh, first thing to do is get a second opinion if it bothers you but Dyno's are notorious for odd numbers and best to compare figures from same car same dyno, use it as a comparator rather than a set in stone performance bible..
Often a 2WD dyno will calculate 4WD cars but the figures for 4x4, Haldex 4WD and permanent 4WD vary hugely not to mention Auto/Manual and DSG as well. All these will give a different loss in the drive train.
I started to question my figures looking at yours, i have 251whp and 375 bhp corrected to 381bhp. so a large gap between whp and bhp however the thing goes like scalded cat and is struggling to put the power down even with ESP engaged. Glued to the tail of a 4.5ltr V8 maserati last week i was more than happy. Truth is with his 450bhp and i suspect quite a bit of extra weight , once you get to these figures you need big differences to make noticeable differences IMHO. wind resistance and drag/weight is your real enemy .
If you take a car that does a standing 1/4 mile in say 13 seconds say a manual S3 you would need to add about 10 rwhp to knock 1 tenth of that time. but a car doing a 10 second 1/4 mile would need 15whp to knock a tenth off its time.
What i am getting at is you could be 40whp down on the car in front but cross the line just .3 second behind him which you are going to say was pretty much a dead heat.
Starting to rabbit now so i will shut up