2015 Ford F350 6.7 Diesel Daully. Knock in motor from cyl #8. Cyl 8 misfire codes. After a tiny fuel fire under plastic manifold. The TURBO sucked plastic into cyl#8. I removed glow plug, then ran the motor, knock sound went away. Put glow plug back in not came back. Someone with mechanic skills would have a nice truck after repairs ! This is a $40,000 truck if you can get the knock to go away. All 7 cylinders are around 420 compression. Cyl 8 is around 270. Prob melted plastic on valves. Compression in cyl 8 holds! Does not bleed off. I have a new truck already. Don't feel like working on it.(Brand new parts-> HP fuel pump, disaster prevention kit, EGR, fuel filters, brake vacuum pump, injector fuel return line, Intake manifold, turbo boot, hp fuel sensors, wiring harness) $15,500.