Good to see someone else finds this too. I have heard it in the States that it happens on the 370z too. When we had a RR day at Surrey RR, I think they did the pulls in 3rd gear for some and the numbers didnt seem right, but they assured the members that wasnt causing it. When I had mine on a DD dyno at Eurospec, my car made spot on numbers for what I was expecting with a plenum spacer, came out at 240WHP with nice flat torque curve, so stock I guess it would have been 10 or so HP down - if mods claimed HP are to be beleived
Thats surprising, i and many others find SRR to be about the most consistent and genuine RR, IE they don't tailor results to keep owners happy, i know of at least four other car clubs that only use them, plus a couple of well respected mappers.
As Mark said, its down to knowing the car. Now we know you need to do a fair few pulls at WOT (5-6) before doing a final pull, we can let any dyno technician know that and they know for in future. When we were at SRR last time, I think most cars only got 3 or maybe 4 pulls. Intersting to see it can cause different results though Not at all saying SRR were at fault btw, they did everything right on the day, just shows you need more pulls.