I'm trying this stuff out because I heard it was great stuff. I'll post you guys with the results. I'm also trying Redline's 10W-30 Synthetic. What's the best oil filter for the WRX?

The 75W90 NS is one product, the Shockproof is something else. The NS is a GL-5 rated lubricant and as such meets the specs for the trans, Shockproof is not GL-5 and in fact Redline does not recommend it for street use. There are some people using the Shockproof either straight or in some mix with other oils (generally Redline) and they claim better shifting performance, but it may not in fact be better for the transmission. Just be aware before you change your trans oil.

Use an OEM filter, it's actually very good.