Slow in, fast out. It is possible you're driving the car just right at one of your first events, but that doesn't seem to be usual in autocrossing. First, get a good alignment. Then work on driving. If you want to spend some money on the car, that's fine, but realize that you'll get more time from working on the driver.
I just did an autocross and rode in two other STis (who both ran novice last year). Their biggest problem was going too fast in the corners, leading to various degrees of scrubbing and pushing, which means they can't get back on the throttle coming out (they also didn't unwind and back off). I think corner exit is our car's huge advantage over the others, and if you're going too fast in the corner, you just push out on the exit which means you can't get on the throttle. This isn't the car, in my opinion -- heck, my loosy goosy Miata would do it if you went into a tight corner too fast. Number two for them would be looking ahead -- that cuts down on extrenuous steering inputs and exiting a corner pointing in the wrong direction.
I'm trying to be helpful. I found my stock STi with a good alignment to be pretty nice. It didn't rotate, but it did nice drifts under power. The only time I recall it plowing was when the driver (me) screwed up and didn't slow down enough for the corner. Amazing how much times drop when you can go just slow enough in the slow parts and fast in the fast parts.
Regarding alignment, do some searches. Didn't some of the national guys in WRXs run 0 toe front and some toe out in rear to help it rotate? Max front camber -- mine only made it to -1.2 stock. Obviously max caster.