Im lost!

I bought a 2004 F50 CC with in February. Since that time, have had the turbo off and cleaned since it seemed to have a bad case of turbo farts (figuring sticky turbo). Truck did fine after that, but now is either not engaging, is slow to engage or does not engage at all. It has also started back with intermittent turbo farts when really getting in on it. I am beginning to wonder if I will ever get my boy running like he should. He now has 120k miles. I have already cleaned the EBP sensor and have a replacement on standby. I have an appointment with the mechanic to drop off for new turbo, but want to make sure this is the right direction to proceed in before dropping the bucks. Any help is appreciated. I feel I have done everything possible.