Frankly, installing a separate Internet connection for managers only sounds like you’re trying to please management so that they don’t notice that you have a more serious problem.
I’m not sure what you mean by “wireless server room”, but it implies that you are running much of your infrastructure over wireless. This is not good for several reasons: security, performance, control to name 3.
If you are in a place where you must use wireless (for example: old buildings that you can’t rewire), then I’d suggest that you use some of your wireless equipment as a backbone on a separate channel (at least 3 channels away from other equipment), lock down access to the MAC addresses of the other backbone equipment, with a good encryption key, minimal power settings, and directional antennas to keep it separate.
In other words, design your wireless links using a similar architecture to a good wired network where there is clear separation of communications links. My best guess for right now is that everyone is stepping on everyone else’s feet so to speak. You need to clearly separate functions and areas.
Also look at channel spread across floors of the building so that each floor has its own channel, and use horizontal spread antennas (I can’t think of the right term, and it’s not polarization) to keep one floor from interfering with its adjacent neighbors. Also consider separate SSID’s and encryption keys for each floor.
This is not a trivial problem, and I don’t pretend that I’m giving you the solution, but this should get you pointed in the right direction.