Hi OM, vids look ok and should give you the info you need, glad that the shop agreed that it was probably just crud in the carbs and the exhaust that needed sorting, as you say just find the exhaust leak and bung it up temporarily for now that should make it much easier to sort out the running probs, I know in the vid the guy talked about carb cleaner and it's really important that you do not get it on the gaskets or seals as it will eat them away and then you will need a carb kit to repair your mistake, they are expensive for what they are so just be careful splashing this stuff around. If you have the manual for the bike just follow the instructions for setting the needles to sea level or normal running, as your going to have the carbs apart anyway it will just be remove the clip on top of the needle and move it up or down to the place it should be for your location, be careful when you take the clips off as they can jump off under tension and disappear without trace over the horizon, also be careful when putting the diaphragm back on that you don't trap it in the joint between the carb and the top, just do it up loose first and try the slide to make sure it runs smooth before you tighten it down. That's enough for now hope you get it sorted and get to ride before the summer ends.