has anyone had a problem with over boost? i find when im at full throttle and start picking up speed at around 120 - 140km/h the car drops back like a miss fire the same feeling as trac controll anyone had this happen to then before?

Not sure what car you have ?? It could possibly be the ECU enabling overboost function..
Which is built into ECU to save engine.. Another FAIL SAFE measure built in...
If its not overboost ?? It could be spark blow out.. Either close the plug gap or check spark strength.. Sounds like the wastegate needs some attention ?? Check vacuum lines..

sorry got a ba xr6turbo i did get a code for wastegate closed over boosting ever had to free one up before?

If the exhaust has been modified ?? Chances are the wastegate will need some attention to improve flow.. Usually a bigger flapper and porting ???

yeh got a bigger exhaust 3.5 inch. have u had this problem before?

as soon as you mod the exhaust system mainly the cat it reduces the preassure in the exhaust system. this is a very common problem.

exhaust is like electricity, it follows the path of least resistance if there is less resistance to go around the turbine and out the dump pipe it will go that way instead if exiting the wastegate.

the wastegate is designed to take excess gasses away from the turbine at max boost pressure and regulate the speed of the turbine, if its easier for the gasses to go through the turbo rather than out the wastegate you get overboost. with a stock or generic tune this overboost will cause limp mode or boost cut.

theres a company called extreme turbo manifolds who do an exchange turbo housing that has a bigger wastegate installed that allows you to run a high flow exhaust system and still have good boost control.

i can run 17 psi with a flat boost level no creep or spike.