If you never replaced the regulator piston assembly with a newer higher pressure version when you installed the level 10, then it probably needs to be replaced.
If the leaking out the back stops or gets reduced when you turn down the velocity, then you will know for sure that the regulator piston assembly is the problem. The leak could also be a leak around the oring surrounding the regulator piston assembly.
If it is shooting hot all the time when it is leaking, then it is probably the regulator seat oring.
Since you mentioned that it starts leaking when you adjust the velocity adjuster all the way in, then it probably isn't the regulator seat oring. The requirement to turn the velocity too far in to make it shoot is a symptom of bolt stick caused by a level 10 carrier size that is too tight. Or possibly because you are using a bolt spring that is too stiff. If you have changed level 10 powertube orings, then I would suggest adjusting the carrier size to reduce the tension on that oring. Use the largest carrier size that doesn't produce a leak. If you have installed a long silver bolt spring, then you should try one of the gold springs to see if that helps as well, at least for troubleshooing.
Except for the Automag in front, its usually the man behind the equipment that counts.