Now and again in 3rd 5th and 6th I get like a hesitation, boost loss and it feels like the car is straining any ideas thanks

Would help if you explained a bit more where in revs and what speed you get hesitation etc and what sort of demand you are putting on

Its really amazing anyone still has a car this old without the EGR hestitation fix but thats one option, or could be something similar, or maybe something totally different like boost leaks on the intercooler pipes, the oem pipes are known to be weak specially when mapped, is it mapped ?

Has turbo ever been replaced, is it on original turbo and pipes and what miles ?