It is very important that the intake runners on your GL1000 provide a leak-free connection between the individual carbs and the cylinder head. During carb rebuilds, I remove the intakes for individual inspection and leak testing. This is also necessary to gain access for inspecting the throttle butterfly plates and retaining screws as well as the idle nozzles.
However, you probably shouldn’t disturb the bonded rubber connection to the carbs any more than necessary. Remember these parts are 25+ years old and the rubber is not as pliable as when new.