Removal of Exhaust Bolt/Stud on 912

One of the Guru's will give you a definitive unswear - in the interim, the old way was (if thread still good) to use two nuts "locked" together to unscrew the stud. If thread damaged beyond doing this, weld either a nut or a small rod to the stud and turn. 

If heat is required, you will need a gas torch of some type (oxy/acetylene is the best) but great care will need to be exercised to prevent damaging the alloy heads.

A soldering iron will never deliver sufficient heat to do anything much more than solder or melt plastic.

https://www.amazon.com/Spurtar-0-2-Inch-Stud-Extractor/dp/B07B3S1CJN/ref=sr_1_11?crid=16KAZ2Q2YIRT&keywords=stud+removal+tool&qid=1653827654&sprefix=stud+r%2Caps%2C121&sr=8-11

You will have better luck with a hot air gun and a stud extractor. Before pulling tap the end with a small hammer and it may break loose.

This will work,

I would take a die and re-thread the stud. Then put on the double nut. When it comes time to turn the stud out use the wrench on the inside nut. Then I use a small butane torch to heat the metal around the stud nice and hot. Not the stud itself. You want the meat around the stud to expand. This is why I'm not partial to a heat gun. It heats everything. The butane torch can direct it's heat to a specific spot. Then before you use your wrench tap the end of the stud with a hammer. Don't try and kill it just rap the end to hopefully break any corrosion loose securing the inside threads. 

Can anyone give me some safety tips?  Torches around fuel lines seem quite dangerous.  Obviously I will have to remove them and  shut off the fuel.  Would you advise me to drain all of the fuel as well remove the fuel lines?