whats the difference?

what is the difference between the h22a1 and the h22a4? And what is ATTS? What does it do?

I think it has to do with 92-96 VTEC and 97-01 VTEC preludes. :)
You do the math.

ATTS is Automatic Torque Transfer System. Basically when going around a corner, it makes the outside wheel turn faster and the inside slower, making it handle better. I'm pretty sure there's more to it then that, but that's basically what I've understood it to be. Anyone feel free to add/correct me.