Luckily you have a 4L80e, if a tank had to use a truck transmission it would be the 4L80e. A shift kit would make it even stronger but its not immediately necessary like on the 4l60e. As far as the engine goes, a lot of people upgrade the injectors. It allows for more boost and shorter duty cycles. Also the intake on the stock GenIII engines tends to lean the rear two cylinders out a bit, but the LS6 intake will not, so thats another popular mod. The SC will be bad-ass on that LQ4, lower compression engines alway do great with boost. You might also consider switching to a lower temp range spark-plug. Fully synthetic fluids if you aren't already running them. Those are just some ideas that come to mind.