go buy a couple bolt extractors (aka easy-out), and the proper sized drill bits for those extractors. you will of course have to take your manifold/turbo assembly out of the car to do it, but it's not that hard to DIY, especially on the 2 you said that broke. while you have all that out, replace all of your studs with new hardware so you're less prone to have another one shear on you.
Yep that's exactly what I came up with today as well. I bought the extractor bits today so I'll just get my hands on a new hardware set and do it right. Too bad I don't have a few bucks laying around for a new manifold while everything is apart.