after testing with all various Advanced Parameters of 1704 wireless --- i tried to fetch the BASE OEM Driver Package - i.e. Broadcom 43142 --- below is Link to download the same - and after installing - all bandwidth and low range related issues are resolved (in the Default installed state - so we neither need to alter any Advanced Parameters of Driver Module nor Disable Bluetooth integration on this STA)
http://support.lenovo.com/en_US/downloads/detail.page?DocID=DS033286
Lastly - I must appreciate the PATHETIC JOB that Dell Driver Developers do while simply modifying an OEM Driver Package SDK --- Kudos to LOL DELL Drivers.
Regards