Range Rover Sport TDV8 Limp Mode

Help needed my poor Range Rover isn't running properly it started a few days ago , I notice whilst going up a small hill black smoke the it went in to limp mode 😢. This happened around 6 times it went in to a local garage today for them to put on the diagnostic machine and fix. They have inspected all breather pipes and the thought it was the EGR so they cleaned it. But now the car is worse then before it whent in and the smoke is a lot worse ??? On the bill they've put an advisory which says The vehicle has a power link fitted which may cause over fueling and smoke when accelerating ?? Evan though this has been fitted over 2 years and never had this problem before ??? Has anybody had the same problem or any ideas what's causing this problem thanks inaddvance 😉

It sounds like an EGR valve sticking open or a split boost pipe.