I had the same problem with mine after I got it on. I simply took two #8 7/8" pan head screws and screwed them through the coupler and into the air hat in two places to keep mine on ( having two screws visible like that isnt a big concern under my hood )
I had also thought about reinstalling the factory air hat since it has a raised edge on the intake, but wasn't handy at the time and now that I think about I'm not sure if it is the same dia. as the 360* power tube. So you might want to whip out ye old tape measure.