@guile.
I had a similar issue, or thought I did. But I kept spraying WD40 on the bolts over the course of a few days and they came undone surprisingly easily.
In the UK they salt the roads every winter so corrosion is a major challenge. My 500i was a basket case when I bought it and was 11 years old and the nuts were really rusty. However I cleaned them off with a wire brush drill attachment first and it’s all turned out ok now.
Mechanically these things are better than you might think.
I’d give it a shot at using some anti-seize on the bolts and have a crack at getting them off. You may be pleasantly surprised. If a stud snaps or you round a nut off, you always still have the option of cutting the pipe off and jamming a bolt in, if that way would be an option for you. (It wouldn’t for me).
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