i have bbk long tubes and y pipe

 

5.3 heads (ups the Compression Ratio) 5.3 intake if you have the clearance (flows better then ls1 intake) and run a LS6 cam.. JMO

Edit: a lower set of rear gears will wake it up also.. But head/intake/cam combo is a must for a healthy set up

 

As said above head/cam/intake set up. Adding a LS6 or even a FAST intake on a bolted LS1 is not going to net you much if any torque. You will notice a slight gain in horse power but torque will stay about the same or may even be a little lower.

If you are looking for low end power gears and a convertor will make a huge difference. Even a small convertor with a 2400-2600 stall makes these cars run like a hole different animal. Now add a set of 3.73s and good tires and they strait up rocket out of the hole.

Ditch the SCT as the are garbage generic tunes that will show little to no gain. Your best bet would be a Head/Cam package with something like a 228/224 on a 112LSA or even 111 LSA and a dyno tune would be a great combo for torque and horsepower.

The two other expensive options you have are the TTI 62 trim turbo kit (if they still make it) or a magnacharger set up. Both will make explosive torque but you better be ready to back it up with a built rear end and a built transmission if your running a auto.