make sure to use a ball-peen hammer, as a hammer used for carpentry will break from the harsh metal to metal contact.
That said, use PB blaster (or equivalent) and soak all sides of where the turbo meets the elbow, and also around the studs poking out through the elbow. Let it soak in. Do that a few times. Then hit it with your hammer around the seams (turbo to elbow, but on the elbow), and around the studs. if you choose to hit the studs, make sure to have a nut on the stud so that the nut is taking the abuse and not the stud. You don't want to fubar your threads