Get JPO (the latest froyo) from samfirmware.com, and flash it using ODIN. (use vol down+home+power button when turning on your phone to get it into download mode).
In my opinion, no lag patch is really needed. Lag patches can cause long term maintenance issues anyway still (and you need to take more precautions, such as DEFINITELY keeping a copy of /efs if you use a lag patch). If you are consistently getting excessive lag in late roms, it might be because certain programs you have installed are causing problems (also consider trying launcherpro, or a stock launcher).
If you want a bit more speed, wait for Tayatuma to update his superlite rom, to use JPO rather than JPM, or wait for another AOSP ROM such as Cyanogenmod (AOSP is closer to the experience google wants us to have, rather than Samsung).
Ensure you use a i9000 rom too, and don't accidentally use a i9008 or other model one. Good luck, and remember, this is just my opinion. Also, don't get too caught up in Quadrant. It isn't accurate, and some people here SERIOUSLY (I kid you not), are selecting roms based on a difference of quadrant speed of only a few points (less than 5%).