i got a t25 with no intercooler and its getting 4.5 in 2nd and it starts to take a dive at 5500 rpms and by 6000 its like at 1-2 psi. 3rd gears it does the same but with 6 psi to start with. i got couple really small pinhole leaks in the piping, would that be the cause???

 

probably the leaking. think about it........your piping holds your boost man!!!!