Hi guys. Just took the wagon out for a drive last night. It's done this every now and then, but seems to be a intermittent issue. It seems to happen when I'm at about 3/4 throttle. Not "floored" but more than light/half throttle. The car will be going, and suddenly stumble, and make a muted "pop" sound. It will then kind of "clear its throat" and keep driving along. Anyone else had this issue, and what's the possible fix? Thanks in advance.