Loose Low Speed Needle Valve on MVVS .40
I noticed on my GRRT it did the same on my high end. All I did was take out my needle and cut a small piece of fuel tubing and stretch it over the needle and put back on the carb. It was a pain to stretch over carb input for needle but once on it kept from any leaks and any movements.
Give it a shot it worked out for me.