no power,builds boost wastgate opens eraticly

[mike187]

i just finally got my car running again,the engine just got rebuilt and i sent it to the tune shop, i have a 89 240sx with sr20det,upgrades apexi power fc with map sensor,550 injectors,t3/t04e top mount turbo,38mm external wastegate,graddy profec b spec 2 boost controller,so long story short the tune shop tells me my car is creating 105 hp at 8 lbs and 169 hp at 18 lbs,very weird,there explanation was i needed a new turbo,this doesnt make sense to me cause if its hboosting 18 lbs or more i dont see how it can be bad,i got the car back and noticed no matter where i set my boost controller the wastegate will pop open around 6 psi and will open n close eratically as it goes up in boost,i dont bleave its the boost controller because when on the dyno they were using a manual boost controller and it was still occuring,the boost controller is set up right and i removed it and the diaghram is ok and spring which is blue which i bleave is 7lbs which the boost controler should compensate for,im totaly mind blown on this and have no answer and have a hard time beleaving its the turbo,the tune as wel as everything else seems to be good,thank you for any help and feedback