I should add that I was one of the ones that had that lag issue with !bw with ioBanana.19.full. So it's possible that you've found & squashed the bug that was causing that although I couldn't say for sure as a lot of my config has changed since then including hardware. Back then I was using:
AMD Athlon XP 2200+
1GB PC2100 DDR
2 ATA-133 drives in RAID-0 config running OS
1 ATA-133 drive running site
It caused cpu to go 100% for abt 20-30 secs...hope some of this data helps you with that problem.