Any updates? I’ll share my recent situation with my 1998 Dyna Wide Glide stock engine with a Mikuni also. I was on the highway going 60mph and my bike started stumbling, didn’t want to run under a load but idle and reving in neutral or with the clutch in was almost no problem. It has been doing this at times before but it would always go away and I just wrote it off. I looked all around for any clues and found nothing. This time however I was on my way to OC bike week and it didn’t go away for the most part. I was getting low on gas so I filled it up and didn’t have a problem again. The whole time riding I was able to think about it and I figured it had to be a gas flow problem or at least that’s what I thought. Didn’t matter if the petcock was on reserve or not. I ended up at the local HD dealer and while they didn’t have a new fuel filter for my bike, I asked them to remove the petcock and check my filter. They did and it was covered with peelings of my gas tank liner and restricting the gas flow. They cleaned it up for me and I had no more problems so far. Now I’m researching how to reseal my gas tank which I’ll probably do over the winter. I’m not sure what your gas tank has inside for a filter, but you may want to check that out.