I wouldnt trade but thats just me.Just step up to a cheap convertor if you cant live with the stall.Trade it,and youll be buying another one day.Im going to be using a Garret ta61 with the stock convertor.
I have the gt-61 with a stock conv. and it sucks. 60 ft with stock turbo is 1.77, 60ft. w/ gt61 is 2.0 with stock conv. get at least a 3200 and be done with it.
by the looks of your sig....a turbo is the last thign you need....sorry, i dunno i wouldnt be surprised if you could get 650-675 considering them new are around 750, however most new ones come with warranties i believe...but i may be wrong