I've actually seen the Redline 75w90NS make the 3-4 shift worse on early WRX boxes.
Also here in IL when it gets really cold all the redline gear oils (except mt-90?) look like pudding when I open the boxes up.
Glad to see you guys are getting good results with the Valvoline 75w90 syn. We run it in every box we build from stock to PPG's and have never had an issue.
Dylan @ DS1