so I figured out the problem - thanks to good old google! found a thread about some guy's WRX with the same problem, he got new tires installed and car started wandering.
sure enough - my front tires are quite new (like this when I recently bought the car) and rears fairly worn.
A quick Tire swap front-to-back and the wandering is gone!

Car is high speed very stable and handles beautifully.
(that said I did still inspect shocks and some oil leaking at front - although the bounce test reveals they are still absorbing shock well)