Performance issues with flashed 7800GT (G5)

Hey,

I recently flashed a PC 7800GT with the 128K OEM NVidia ROM. It's one of the cards with a physical 128K ROM chip, so no worries there. However, it doesn't deliver the performance I expected. I have a Late 2005 2.0 DC, 10GB DDR2 and use Leopard 10.5.8.

This is what OS X puts out (german):

NVIDIA GeForce 7800 GT:

Chipsatz-Modell: GeForce 7800GT

Typ: Monitor

Bus: PCIe

Steckplatz: SLOT-1

PCIe-Lane-Breite: x16

VRAM (gesamt): 256 MB

Hersteller: NVIDIA (0x10de)

Geräte-ID: 0x0092

Versions-ID: 0x00a1

ROM-Version: 2152.2

Performance issues are: I can't seem to reach frame rates that are anywhere near the results provided by barefeats. Quake 3 runs with approx 200fps in 1600x1200x32 (I expected 300+ fps), Quake 4 and UT2004 run okay, but not on high settings with high resolutions. So, not equivalent to what you wouldd expect from the system's specs) Same goes for Colin McRae Rallye. Now, I remember reading about performance issues in 10.5.8 with the flashed ROM since it doesn't seem to be a 1:1 copy of the original one. I didn't try it in Tiger since I don't exactly want to go back from Leopard. Am I right that this is probably an issue of the "OEM ROM" (from the macelite)? Does anyone have the real deal in terms of 7800GT ROMs and could provide me with a link?

Br