GT15 Turbine Housing Stuck

I'm rebuilding my GT15 off of my 175k mile Passat, and I can't seem to get the turbine housing off of the center cartridge. I've scoured Google, and all I can find is "hit it with a hammer" and "soak it in penetrant" which I have been doing for days. I tried heat and penetrant. Still nothing. It's just so small.

It's almost as if the housing has rust-welded itself to the cartridge. Should I go buy a wire wheel for my Dremel and do some extreme cleaning around where the two pieces meet? Find someone with an oxy torch?

I know a lot of you think the GT15 is a throw-away turbo, but I can't justify spending the money on a K03/04 if I can just rebuild the stock turbo. It's destined for my EuroVan.

1:1 ATF and Acetone. Dont use plastic bottle. The best rust eater out there is sold from tractor supply. I dont recall what its called but its in a while can with black lettering, its got sculls and crossbones warning on it, its a heavy acid for rust resolving in the field on old equipment. DO NOT GET IN YOUR EYES, wear safety glasses 100% or you can go blind from this stuff.
If all your bolts are off the turbo it should come out. Soak it overnight in a bath of 1:1 acetone and AFT mix. Then tap it with a hammer. I HIGHLY suggest you use a dead blow hammer mallet. they are cheep at harbor freight.