GReddy Turbo Timer Problem

[ETTInnov04]

After taking a joyride with a friend and his mkIII supra we stopped and I realized his car ran for like 7-8 minutes, while mine ran for about 2. We were both pushing our cars pretty hard and we drive about the same. I understand his car works harder but still thats a lot of difference in time.So I decided to check the settings on my turbo timer, my rpm's weren't reading correct. But when I set them exactly the way the book states it was off even worse. Now at idle it was reading 2000rpm's. Any ideas? I was planning on calling GReddy but figured maybe someone had this problem before.