Dyno'd car today, Having problems with boost please help!

[ask52]

Hey guys I went to the dyno today (dyno jet) To see what the power was. Also I have been having troubles with the boost falling after 4800 RPM. These are the mods

redtop sr, fmic, greddy bov, turbosmart dual stage boost controller, electric fans, megan ss header, 3" turbo elbow, 3" exhaust no cat, K&N cone filter, stock t25.

The car boost's 15 psi right up till 4900 RPM then falls to 8psi (it falls right away not gradually, almost like some one hit a switch). @ 4800 rpm its at 200rwhp. Then it falls to 180 and slowly goes up to 211rwhp @ 8psi around 6500rmp. They did 4 pulls but could figure out what was wrong. They emailed me the dyno graph and you need the dynojet software to view it or I would post it up. Any ways I went home to try to figure out what was wrong. I test the ic pipes for leaks and nothing. I then pulled the line off the waste gate and plugged the vacuum line from the engine. I went on the high way and slowly got the car up to 4500rpm with out boosting. The I opened it up, The boost hit 15.5 psi and smoothly fell to 12psi @7000rpm.

So now I don't know what is wrong. I'm guessing that the t25 is just not big enough to hold 15 psi all the way to 7400 rpm. But why does the boost fall so fast with the boost control hooked up? If any one has any ideas please let me know!

Thanks...Josh.B

P.s We check for exhaust leeks as well and there was nothing.