I don't think there's dyno-backed answer to your question but it will be insignificant change that you won't feel from everyday driving.
I agree with the other posters in assuming that its around 242 with 91. I only have 91 available to me, and there is a perceptible difference in power between 87 and 91 once you get into the higher RPM range. I don't have any data to back my claim, all I can say is that I can notice it, so take that for what it's worth.