power products for '02 Avalanche

Just took our new 28' Prowler travel trailer (5200 lbs dry) out on the weekend. My '02 5.3 Av (410 rear end) pulled it fine, but a little more power would have been nice around some of the hills here in Southern
Alberta. Any suggestions on power products would be much appreciated. I figured I got 11 miles to the gallon so any tips that could boost that by a couple miles would also be appreciated.
Thanks in advance

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