Good job going for more than a t25. the efficiency range for them sucks past 240-260 whp. plus you wouldnt get 250hp on the 7 psi spring the wastegate holds.

as i read your post, i saw you were asking about the t28. mine holds a steady 7 psi, but sometimes spikes to about 10. i think some of it has to do with outside temperature and atmospheric pressure, as well as the humidity. than again, i dont drive it everyday to really pay attention to it.