Go to Home Depot (or the like/similar) and purchase a Map Gas Torch(not propane). They are usually about $40. Just be exceedingly careful in where, and how you point/use it! You might consider installing a header(NWOR or the like) if your going to that level of repair.
With the torch, you can heat the hardware up to where it is almost red, or changing color and usually, it will roll right off. If it starts to bind, reheat it again. When your torching things, try to only hit with the flame and heat, what you want to remove itself (ie only the hardware, not an alu head, or sensor/wiring, etc....). Otherwise, you might end up damaging something else in the process. Best of luck with it.
regards