Look up Gray Guns. he is famous for his work on Sigs and HKs. He has a mod for the older 220s with the internal extractor. Not cheap or fast but high quality work. Bruce Gray is the man for this issue. HTH.
Think about the different stages in the firing process. A Failure to Feed should not have anything to do with an extractor.
I would look at the feed lips on your magazines that they are possibly too open and are allowing the rounds to come up too high and jam into the top of the chamber.
The pistol FTF with all three of my magazines. Do you think that malfunction is still mag related?
The pistol will do FTF with Federal 230 gr HST and WWB 230 gr. fmj?