Pull the upper and lower intake manifold off and pop the regulator out and see if there’s metal on it.
Also I’d cut the oil filter open and search for metal because no cp4 is going to lock the engine up. Any time I’ve heard a 6.7 make noises like that it got an engine. However, I had an lml that the customer said it squealed as well prior to dying... it’s currently getting a fuel system. Cp4 had come apart.
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.