Standard cars tested on various rolling roads round the country, have so far indicated that they produce between 255-265bhp. They tend to be less bhp for the first 600-800miles.
Mine was run on Awesomes RR, 1 week after i got it, with nearly 300miles on the clock. It had a tank of supermarket special the dealer had put in it. It produced pretty much bang on 240bhp.
I went back just over a month later, with just over a 1000miles on it, with the car only being fed Shell Vpower. It then did around 260bhp. Same rollers, same settings pretty much same conditions, and from experience i know Awesome have good repeat results, never much more than -+ 5bhp either way.
The car did get quicker and more free revving once it had done over 800 miles, we think something is built into the code to make them run a bit rich for the first few hundred miles to
help them run in and coke up.