I've had mine rolling roaded quite a few times to keep an eye on my mods.
Stock - 148 (spot on the standard figures from Ford)
Panel filter - 151
K&N 57i induction kit, Milltek flexipipe & cat back exhaust - 167 & 168
I think I have been quite lucky but I have used the same rolling road, same fuel for all those except the 167 when I decided to double check & see if Janspeed gave me the same figures as my local rr (whats 1bhp between friends? *heh*), which they more or less did.
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24/03/05 to 27/06/12 & I loved it