It sounds a lot more like a throttle body issue to me. This engine seems incredibly prone to throttle body issues if they aren't kept clean. I knew this when I got mine, so I haven't had any issues, but I wipe down the throttle plate and bore at every oil change and pull it off to clean it every 30K.
That sounds like a lot, but what's happening is the carbon is building up on the bore, which causes the plate to not return to the closed position completly, which in turn sends a wonky reading to the throttle position sensor. The TPS uses a potentiometer where metal fingers glide over a PWM-controlled film. When the idle fluctuates (slightly), it wears a groove into the film, and the fingers "hang up" on it, causing issues at start up/acceleration.
If you clean the throttle body early and often, you can seemingly avoid the problem all together. Once it starts, cleaning works for some people, not for others.
There's no guarantee this is your issue, but I'd definitely clean the throttle body ASAP and see if it fixes the problem. Your best bet is to remove it from the car, which is really easy (a couple of bolts and hoses), and clean it thoroughly. Just make sure to position it so that the electronics are in the UP position when you spray cleaner in there. You don't want to get any fluid going into the throttle position sensor, which is attached to the TB.
