I can speak for my own results though, and they contradict yours. I posted anywhere from a 5-10 FPS gain upon first using PyFFI on the vanilla meshes.
In which locations? Your system info? Maybe not every nif is optimized as well as can be and some of them are degrading? I'm ready to help to improve optimization algorithm not only for new systems, but also for old - in this way it will be effective for everyone. You actually are damn sure that you have gain everywhere and dont have lower than vanilla perfomance in some places?
Ironically, this may be why you're seeing degraded performance. Oblivion is an oddball, disabling some things can actually harm performance rather than help.
Tests were ran with exactly same config.
You are using a configuration that was horribly out of date even 5 years ago, and as indicated is based on AGP, with a shared memory pool. How can you honestly expect those results to be of any value to people who are using more recent hardware?
AGP is not bad as you think. Many current-gen mid-range cards were released on AGP - Radeon HD 4xxx series for example. AGP memory is not used at all if a free vram remains, so while everything is stays in vram, agp memory pool isnt active. I can even disable it completely and test again if you want. 5 years ago it was a mid-range config, cept for processor. Check system requirements for these games (random pick of highly rated games back then, which I've played): TrackMania Sunrise, SpellForce: The Breath of Winter, Need for Speed: Most Wanted, The Movies, Splinter Cell: Chaos Theory, SWAT 4, F.E.A.R., which has been released in 2005. SpellForce: The Breath of Winter for example.
Hardware Requirements
Intel Pentium ? III 1GHz
256 MB RAM
3D-Graphic card with 32 MB RAM (compatible with GeForce2 or better)
Windows? 98, ME, 2000, XP
DirectX?9.0a or higher
2 GB free fixed disk storage
Recommended
Intel Pentium? 4 1,8 GHz
512 MB RAM
3D-Graphic card with 64 MB RAM (compatible with GeForce4 Ti or better)
2 GB free fixed disk storage
Windows? 98, ME, 2000, XP
DirectX? 9.0a or higher