I don't think the whining noise has anything to do with the anti-gurgle kit. My 300E gurgles, but I've just never worried about it. The whining noise probably has something to do with the fan, the gurgle comes from coolant gurgling through the heater core or associated parts. The fan and coolant flow have nothing to do with each other.
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in