What is the best Mod Chip for PS2?

Depends on what version of ps2 you have. For the slims (v12+), I would reccomend you install a duo 3 ultra or one of the modbo chips. From what I hear, crystal chip 2 sle are good as well, but I think they are not being produced any more because my supplier has been out of stock for quite some time now and their site has been messed up for a while. It was origianlly meant for homebrew but someone hacked their firmware for it so it could run backups. For one of the fats (v1-v11), I would reccomend a matrix infinity or duo 3 ultra. Duo's are great because they are cheap and work on any version (modbos do too), but they might not be the best choice for one of the older ones. Modchips are very very hard to install on a ps2. The points are very small, and you can mess up easily. I would use a magnifing glass, especially when soldering onto the bios. If your bridge 2 or more pins together, that would be a very bad thing. I would reccomend having it professionaly installed if you are not good at soldering. You probably wouldnt wont want to break your ps2.