I've tried your BIOS on my P4C800-E Deluxe rev 2.0, but I'm not able to change memory timings: even if i set tCL to 3T, it stays on default 2.5T (same for tRP and tRCD). I tried both 1:1 and 4:5 with 800 MHz CPU.
Tried to load BIOS defaults, but it didn't help. Do you have any idea what went wrong? I used old afudos 2.11 for flash (if that helps).