if the pipe has come off the rear jet then when you spray the boot lid will fill with water and no water will come out of the rear jet. Does any water come out the rear jet?
If the pipe is split you may get some out the jet and some into the car but i would expect there to be noticably less pressure
this is a common problem (just this sunday i had to put mine back on)
what it is is when the water is frozen in the pipe like it is at this time of year the pipe blows off the end of the connection, and you get no spray and a wet boot...