the adventure begins, *&%@#^ secondary air

should read : Low Emission high consumption Vehicle.
Be careful! The pipes are very expensive for what they are. The new stainless steel ones are way stronger and shouldn't crack as easily as the flex pipe ones.
As for your question, some oil to release the nut might be worth a shot.

Apply some Liquid Wrench or 50/50 ATF & Acetone mix to the nuts to try to loosen things up. Then put a small pipe wrench on the smooth part of the hose to try to keep it from turning with the nut.

A pipe wrench won't crush the hose like vice grips or channel locks will, and grip better.

Try using a small wrench to hold the head nozzle from turning. When I first tried to remove this, the flex hose nut turned and it also turned the nozzle that seems to be threaded into the head, but I believe they are two separate parts. Here is what the manual says: "Loosen 2 union nuts securing air manifold to cylinder head adaptors." So, you may need to keep the flex hose from turning and keep the head nozzles/adapters from turning.