Im in Seattle, but the only LS1 based engine Ive tuned is an 02 5.3 in a Suburban. That said, YES you can make more power with a tune. Surprised you dont have one already, a good tune is usually worth 15-20rwhp! Couple that with an LS6 intake and its probably closer to 25-30.
If you ever make it up to Seattle let me know!
13 Sonic RS Cyber Gray Metallic 6MT, mods in process
08 TrailBlazer 3SS AWD White, modded, dropped, SE22 Performance tuned
02 TrailBlazer LT 4X4 White, modded, lifted, SE22 Performance tuned