From bobey49 via YouTube: GTA 4 is now running cooler than before even though it makes fan noise it really helps my system. I noticed a big difference in graphic performance, faster game play, and hardly no jerking unlike before.
The 19-blade fan is a very difficult to find hardware part in the PS3 as they where only used in launch systems and Japan systems.. after late December all were 15-blade to reduce costs.
The only thing the 15-blade will do to your system is build up more heat while the 19-blade will push the hot air out. I just got my backup 19-blade fan just in case (you never know)... they will sometimes show up on eBay, but very rarely.