Hi. I'm in the process of replacing vanities in my bathroom.

I've opened the wall since I needed to move the sinks.

Discharge line running out of the bathroom is 1.5" Galvanized steel with a right angle elbow where it broke the wall for the old sink. I want to remove the elbow and convert to PVC. However I can't get the elbow off. Tried a pipe wrench and a hammer, then an extension. It is buried amongst the wall studs so access is poor.

Suggestions? I've never had much luck with WD40. Someone recommended PB Blaster anyone have experience with it? I'm a bit worried about using propane torch because of the proximity of the wall studs.