if it's cobb, it's fuel cut and you can make quite a bit of boost from it(upwards to 17psi! i dont' think lc has anything to do with you bogging in 2nd though...
Buy a 2006 sti fuel pressure regulator and install it. Follow the cobb tuning directions on their website for their fpr kit. I am convinced this is the reason for ringlands issues
one of my coworkers has a hybrid build. wrx shortblock with sohc heads and a td04. not sure what he's using for engine management, but its an rs similar to yours