Flat spot at 2500 rpm on Puma

My friend has bad power fade at 2500rpm.Once past there it seems happy to carry on thro the max rpm.Any ideas?

I've heard that this is an issue with many puma's though not mine, I have also heard that B.A.S that's Bell Auto Services have worked this issue into there upgrade and people are very happy with the results, no personal experience with the issue or B.A.S other than a chat with them at a show which was no pressure and helpful, also worth looking on Defender2 - Index

Mark