Engine suffocating

Does the c13 twin turbo have a wastegate? If so, sounds like the gate is stuck partially open. I would check the actuator and the gate.

 

CEL on? Sounds exactly like symptoms when having IVA faults/issues. I would bypass the DOC muffler like @MLC Adventures suggested. The KCB high pressure turbo is wastegated.

 

Sounds like you're having iva issues friend. On another note they do not look like new turbos to me. With core charges and the way parts are rebuilt and exchanged now adays your tech probably wouldn't have just replaced the insides and used your old housings so something is fishy there. Check all your boots to be sure they are tight and no rips or holes. To fix an iva issue you can have them disabled.

 

Caterpillar never made a twin turbo engine.
They have however made a bunch of compound turbo driven engines.
If you don't know even the basics, take it to a mechanic