Holden Captiva 2014: Smoke coming from engine

Driving my 2014 Holden Captiva on the highway at 100 km/h black smoke came from exhaust engine, a loud knocking noise was heard, but no warning lights came on. I could not stop on highway, so drove for 10 min. at low speed – 60km/h – the engine did not lose power or become hot, the noise stopped and the engine ran normally. I stopped in a town and called the NRMA, but they could not help. They checked the car and said it may have been a particle filter burn-off gone wrong. The car was checked at a Holden garage, but they could not find any fault. What is going on? Have you heard of this happening before? Also, the car is now having trouble changing down a gear, and shudders when changing down. What is your opinion?