but its nice to know what boost level you're running. i had to temp. hook one up to see where i was at (currently 11) because i couldn't tell from my stock guage.
anyway, i decided trying the 20w50 upon your rec. in search. sounds like you're having good luck with the oil. i've never steered from 10w30 but gonna try the heavier weight with the new z. i was originally planning on pennzoil 20w50, but found the castrol formula with the same weight designed for the high mileage motors.