Boost problems

[DSMPagano]

Hey names Pagan and i have a problem with my boost. The boost is fine in 1st,2nd,and 3rd but when i get into 4th and 5th right about 5k RPM and about 14-15psi the boost needle starts to bounce and i get get anymore boost. It sounds like the bov is opening up on me, i always let off the gas so i don't know if it will go any high if i really stomp it don't want to though. Its a Greddy type rs blow off valve. I've tightened it all the way to hard. it help a bit but I'm still having the problem. Any advice would be great thank you.
PS. any questions let me know
Pagan

 

[ddavisaf]

First thing's first, you need to run a boost leak test.

 

[DSMPagano]

yeah i was thinken about doing that, but what is stopping me is the fact that i have no problem at all pulling all the way to redline at 20psi in the first three gears its the last too, but when i get home for winter break i will do that boost leak test