Aha! Now that we have clearer details, it makes sense.
Yes, P0406 in dicates a problem with the EGR system.
Yes, since EGR systems include a small orafice that passes exhaust fumes into the engine’s air instream, they can get contaminated with carbon from the exhaust. It sometimes doesn’t take much buildup to make the EGR valve sticky.
Yes, a sticky EGR valve can cause lurching at low speeds. It’s function is to allow a bit of exhaust gas into the air instream to displace a bit of oxygen under heavy load and prevent the cylinders from overheating. At low speeds, if it lets exhaust gas into the instream it causes a problem with the fuel/air metering.
Did he try cleaning teh EGR valve?
Knowing these new facts, I’m not sure you need a new shop. Everything makes sense now.