You can't race your car if it doesn't get there before the event starts.
With the following advice you will have an entire new truck with power you never knew it had. Like dropping a new blower on a well tuned 454 and running it down the track on a cold day vs. without the blower.
The biggest gain you can get is getting rid of the factory exhaust and Asthma Attack factory turbo esp. for towing. Figure at least $1500.00 for exhaust, tune and turbo. The A Team Turbo will pay for itself in fuel saved, less fan use, and higher MPH vs. a factory turbo that overworks the engine. Others can comment on MPG results of other turbo's tried vs. factory.
Otherwise with the factory turbo you keep RPM at or below 2200. Won't do much good to downshift over that RPM as the turbo chokes. Worse over 3K RPM. You simply are fighting the turbo, cooling fan, and hot intake air more than the power generated on a long grade at higher RPM.
There are minor power gains to be had with just a chip that runs more boost. But not much and the turbo keeps your MPG the same.
Don't settle for 'just a chip'.