Smoking problem

Hi I’ve got problem with smoking from my car it Normally happens when it warms up or when I put the air con on in the morning to give me hot air . And it’s a bad gas smell in the car at times and gasing people out behind me.. or when it’s in a high gear. Doing low speeds.  It’s been into fords lots of times. They are very  Quick to charge me money to fit parts that don’t fix the problem.  So far I’ve pad nearly £3000 .. and I’ve not got nothing back ..... it’s had oil change it’s had new egr value.. it’s had 4 new Injectors...I’ve taken it for two terraclean. But the problem still there even day ....I’m Tired of paying for guesstimation’s .. the last thing ford told me was they think .yes THINK !!!! it might be Carbon buildup .. I don’t know what to do with it. Or who can Possibly fix it. it seems like too me people  just want to take my money . I’ve had Enough of paying for guesstimation’s