Hi Julie,
Welcome to TDP forums.
Give us a little more information on your truck.
Year, model, interior color, you know the drill
Two separate issues here:
Dieing. Sounds you like you did the cardinal thing to do in this situation. Change the fuel filter. Besides that it's mechanical troubleshooting. Could be a kinked line, or a fuel lift pump on the side of the engine that's failing causing the dieing down to the injection pump itself. Were you able to easily prime the new fuel filter with the existing pump?
Black clogged intake. Welcome to C-Series 6.2L (light duty 6.2 version) because it has an EGR (Exhaust Gas Recirculation) system on it. In short it eats it's own exhaust at times, which being around Diesel's is black carbon, that of course builds up over time (mixed with some normal blow-by the engine consumes).
I'd say don't worry about the intake condition because that can be upgraded later down the road for a J-Series Non-EGR manifold.
Fix the dieing part first! It ran just fine with the intake is has now before it developed the new problem.
1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
1982 C10 SCSWB 6.2NA, 2.73 700
1986 C10 SCLWB 6.2TD 3.73 700
1989 V20 SUB 6.2NA, 3.73 400
1994 G20 VAN 6.5NA, 3.42 60E
1994 K20LD ECSWB 6.5TD, 3.42 80E
1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
1995 C20LD ECSWB 6.5TD 3.73 80E
1995 K20LD SCLWB 6.5TD 3.73 80E
1996 K30 DRW 6.5TD 4.10 80E
1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway