2001 Silverado 5.3 L

I recently added a K & N cold air intake and went 3" cat back with a Magnaflow muffler. I've got 25k miles on the truck as most of my driving is around town and a short commute to work. I do tow my 16' Crestliner boat with a tounge weight of 260 lbs. about twice a week to the local lakes.

I've gained maybe 1 extra mile to the gallon, but it does sound sweet. My questions are, should I be running any injector cleaner i.e. chemtool b-12? Time for new, perhaps better plugs? The originals are still in there. Any other suggestions to squeek out a little better mileage?

Thanx in advance...Mike

Wow, an older truck with less mileage than mine. I have an '02 with ~28,000 on it.