These railroad puffers?
If it had been a "real" turret and not a dumb weight I could have guessed at attachment points for extra armour but since this is a dummy turret to simulate the weight of the operational one I would say that it is attachement points for the straps/chains/ropes used when lifting the dummy turret on/off the chassis.
As for the things that look like cylinders for compressed gas.
The Germans did use compressed gas (stadtgas, the type distributed in cities to gas stoves) instead of petrol for test and training purposes.
If you are referring to the gas flasks in the image above they do look sort of small for an engine able to power such a heavy vehicle. Doesn't look like fire extinguishers either.
Gas for starting the engine?
Compare with these:
Chassis for driver training running on compressed gas instead of petrol.
Big cats can run on gas too .....
I hope they based this kit on actual photos ....
on a Pz IV chassis