I would pull top of intake, put a bolt, sealing washer, and nylon nut with red threadlocker to seal the hole once and for all. keep in mind, anything thats loose there gets sucked straight into your wallet.
Drill/tap as best you can for a threaded stud, locktite the stud into the lower intake, then pass the stud thru the upper & put a nut on the stud clamping the upper to the lower