ECR033 is right. I have similar power to him with standard internals, and I track my car.
Your problems seem to be tune related, and this business about not fixing the exhaust manifold properly because you didn't have enough money seems really silly.... If you have enough money for a rebuild, you have enough money to fix the exhaust manifold.
If it's warped, then it's leaking, and that'll cause you some issues.
Just get a leakdown test and compression test done. If all's good spend the money on fixing up that exhaust manifold, buying a new turbo and getting it tuned properly. You should easily get to 250rwkW and not have any issues with the engine.