Best place for that BOV is back in the packaging it came in. Seriously not a good idea on these Bosch ME7 cars. The EMS does not tolerate BOV well at all, more trouble than it's worth by far. These cars utilize a Compressor Bypass Valve that recirculates the excess pressure back into the intake post MAF to prevent altering the air fuel mixtures.
So you want the car to go "whoosh" right, to let everyone and their mother know you have a turbo right? So best way to achieve this is with a cone filter in place of the stock air box. If you want louder, more complex venting noise than the stock CBV you can try a Forge piston type CBV like I have.
That's what I did: Cone filter, Snabb Pipe, Forge CBV, Hood liner removed, rubber rain seal removed and hood vents installed makes for a very loud accelleration and venting noise. And ME7 is happy to boot.
By boost going down what do you mean? Do you have a boost gauge hooked up to monitor boost? If so whats the vacuum number at idle and what the boost readout at top end? If your experiencing lost boost replacing the cbv would be a good start as well as getting a new turbo control valve (tcv). Snabb and Ard both just came out with one, basically the same tcv just different names on them. you can still buy it for sale pricing at snabb i believe http://www.snabb.us/Snabb-Precision-TCV_p_134.html. You will also want to check for any boost leaks this can cause a loss of boost.