Whistle from manifold

Hi, having dealt with the warped manifold issue last september by purchasing a machined flat item with the webs taken out and replacing one stud that had pulled out with an m10 socket head bolt everything was rosey in the td5 garden once more untill 4 weeks ago when the stud below the original one started to come loose and cause the telltale whistle under accelleration. Again i drilled and re tapped for another m10 and this time i used an after market manifold gasket from rimmers, now its whistling again i have checked the bolts and they are tight ( this is blowing at the end next to the bulkhead where i have replaced the manifold studs) Is it the manifold gasket quality or should i use some sealant when i redo the gasket?
Andy.

Did you check the condition of the surface of the engine? That manifold mates to just seems strange that the manifold lifts in the same place.