So I have a fairly decent gaming machine that more then bests the recommended specs for Oblivion, but when ever a clift racer spawns near by the game slows down to a crawl!
OS : Windows 7 SP1 x64
CPU : AMD Phenom x4 965 Black Edition (3.4GHz)
RAM : 16GB G.Skill Ripjaws X DDR3 1600MHz
Video : GIGABYTE GTX 570 Super Over Clock 1280MB GDDR5
Game Hard Disk : 2TB Seagate Constellation SATA6
When clift racers spawn in the area I'm in, even if they're just flying around without hitting anything it still causes lag to the point where the game becomes a slidshow. Its usually just enough that I can still kill them but it takes forever with the low FPS.
Settings :
Textures set to Large
Detail sliders set to max
Exteriour Shadows : 6
Interior Shadows : 10
Max water detail\filtering\reflections
Anti-Aliasing and Antistropic Filitering enabled via nVidia controll panel (x4 AA and AF)
Everything else runs fine and smooth on these setting except when clift racers are present

#1
Might help with Lag Download from www.tesnexus.com
Purge Cell Buffers i did not see it in your load order only
Install Purge-Buffers_Cell Change.esp
Under Nvidia Control panel in Profile Manager for the
Elderscrolls IV Oblivion by it Default is has All Anti-Aliasing turned OFF has been know to cause problems and Nvidia Black Screen with Oblivion
could be worth trying turn off to see if it helps with Lag
Creatures can cause lag and end up Crashing game at times
Forgot If you have not allready installed it could also try 4gig Patch on Oblivion.exe when you run Patch it will ask which file to Patch go to your Oblivion Directory click Oblivion.exe