I also heard that the current Vactra formula is not the same as it used to be & others have found the equivelent formula that's is called a different name. No big deal to me though, I doubt I would really notice a difference anyway.
Yes the Vactra 4 is tackier, it's designed for vertical ways. I've always used Vactra 2 on my mill's vertical ways in the past. It does seep through & out the bottom quicker but it was fine. I just picked up a gallon of Vactra 4 one day just because it was on sale & I felt like spending money. It's going to probably easily last me more than a decade. I do like the Vactra 4 much better for the vertical ways on my mill though, that's really the only thing I use it frequently on.