How can I get more power out of my 5.3 V8
 

you can go big and buy a supercharger, or you can add several upgrades to add power, but your best bet for price is intake, exhaust, and tuner

i agree with skeeter, intake, exhaust, and tune should give you plenty of extra power and sound. Not sure how an aftermarket intake would have zero effect on the alpha. is the stock setup that good? i think i do speak for most H3 owners when i say i have no sympathy for your supposed lack of power with the alpha. :D jk.
Try riding in an 06 3.5l haha, i am sick of getting passed by little fuel efficient 4 bangers. it's embarrassing. I also get nauseous when i hear that alphas get similar gas mileage to my anemic 06. But, my intake and exhaust did have a very favorable impact on power and see no reason why you wouldn't get even better results.

I have the flashpaq, volant CAI and flowmaster exhaust installed on my wifes Alpha, and the flashpaq gave the most bang for the buck.

Skeeter is dead on!!!

Here's what I did.....also installed Magnaflow exhaust. Still getting 15.3mpg as well. Not cheap, but VERY effective.:D

Gorgeous truck, great build.

A chip tune and CAI should be pretty effective. Not much else you could do w/o a lot of cash.

Intake, tune (by PCMforless or Superchips Cortex), cat back exhaust, and Efan conversion, can get you stock flywheel numbers to the ground.
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Wake up the 5.3?
 

I did the superchips tow tune, I have to say wakes it a quite a bit, I also did a cat-back results are qustionable but looks and sounds good so who cares and an Airdoc CAI. Overall the tune seemed to help the most and these can be bought second hand for less than 200 or PCM for less tune is 149.00.