Welcome!
Answered your plug question in the other thread on MPG, where you asked the same... bottom line, don't expect spark plugs to increase gas mileage or power, unless they are worn out and need replacing anyway. Do you know if they have been replaced in your truck? At 125 kmi they need to get outta there, if not.
Use OEM plugs NGK DILFR5A-11 (non-Flex Fuel) or NGK DILFR5A-11D (Flex), or what is considered an acceptable substitute by many, NGK LFR5AIX-11.
I will second bender's advice on UpRev, CAI, and cat back, and would add aftermarket b-pipes. The replacement of the restrictive stock b-pipes is a great performance upgrade. None of these will really help mpg... with all in combination, some have reported a couple mpg improvement but I've not seen that. Can't seem to keep my foot out of it. :big_grin:
Cheers!