I’m trying to replace a few exhaust studs on a Type 4 engine and have got one stud that refuses to budge. I’ve successfully removed the others by welding the nut to the stud (the threads were stripped so couldn’t bind 2 nuts together) but this last one is not moving and just sheers the stud off above the weld. I’ve tried heat on the stud (glowing red after welding) and heating the exhaust port (butane torch so maybe not enough heat) and I’ve tried cooling the stud with ice. Nothing is working, not even the WD40 or tapping it with a big hammer. Are there any tricks for young players I can try before I run out of stud?