I say tune it and here's why. Oh, and I recommend a Diablosport tuner because they are easy to use, you can use them to load custom tunes on and they have group of user customizable settings as well.
That lower restriction actually allows for faster air flow. You are getting a bit more air, or shall we say molecules, as the air has a better flow through the system and those little molecules are getting compressed by a small increase in pressure. So...more air is coming in. But it's not a large increase in air.
So there is a change, in and out of the system,and air will be flowing faster and with a bit larger volume of O2 molecules.
But here's something to consider that you may not be aware of...your truck is already running lean because it was tuned that way. The change in airflow can increase that lean condition at higher RPMs. So at Wide Open Throttle your engine runs even leaner and you are on the verge of knock retard, which pulls timing to avoid detonation. So you really aren't getting an optimized fuel burn or performance when you want it.
Tuning your vehicle is done with a programmer and a set of tunes loaded on that programmer. It gets plugged into the ODB II port below the dash and you follow the instructions to load a tune. The tunes you get with the programmer from the manufacturer are called "canned tunes" and you can get custom tunes from various tuners out there.
Honestly, the canned tunes aren't that special. A custom tune, from either Jay Greene or Sean Powell (Hemifever), will really wake up your truck and help get that lean condition under control, optimizing air flow, timing, spark and fuel delivery.
So custom tunes aren't hard to do. You can get it done on a dyno by a trained technician. That is the most expensive method. You can also get them by email and that's the cheaper option. You'll load a tune, log the truck's performance with the programmer plugged in, extract those logs to your home computer and send them to the tuner by email. They will tweak on the tune and email you a new tune file. You'll load it on your programmer, plug that programmer into your truck and download the new tune. You may end up doing this two or three times.
The custom tune I got from Hemifever for my 6.4L CC 4X4 was a real eye opener and the truck ran so much better than stock. I had a S&B cold air intake and a Magnaflow muffler installed, with a resonator delete. There's a little in-cab video I took after I installed the last custom tune he sent me posted below.
Moe's Performance usually has a package deal available, a Diablosport programmer with custom tunes by Hemifever. I'd get in touch with Matt @ Moe's and see what he has going on for deals.
Good luck!
