You would really only notice that it won’t downshift into 5th as often because it won’t lug as much. 6.7s get poor fuel economy generally and if it weighs 10k and you tow with it, averaging 11.5 is totally normal. Most normal unloaded trucks get 13-14. It wouldn’t be worth the money in my opinion.
06 King Ranch
Fass 200, Custom fuel lines, 225/100s, Thumper stage 2 hpop, WPE stage 3 intake, Mishimoto radiator, Flex a lite fans, BPD water pump, MPD oil cooler relocate kit, Intercooler pipes, Compounds built by me, etc etc etc
05 Eddie Bauer
Resealed entire motor @ 170k miles, new lifters, 6.4 push rods, studs, rebuilt the turbo, IPR egr delete, new injectors, new heads, new ficm board, coolant filter, intercooler tubes, regulated return, bunch of other new parts. Factory exhaust, cat gutted(wife's rig). Livewire with gearhead tunes. Should go a while reliably for her!
03 LB7 duramax the "daily/tow pig"
Lbz cp3, s475/stock twin kit, built trans, steel driveshft, amsoil bypass, secondary oil cooler built by me, fass, traction bars, trans cooler upgrade, dual alts, straight center link + tie rod sleeves, efi live, transfer flow/tool box tank, 5er hitch, other small upgrades.. and most importantly, STOCK HEADBOLTS! Just rolled 200k miles, twins installed @ 165k, daily driven on a "550 tune" tows 18k on a "475" tune.