I had a similar issue with my '96 Intruder 150, which is identical to yours. Most likely your problem is just fuel delivery. Did you diagnose all those electrical components and determine they needed replaced, or did you install parts trying to track down the problem?
In my situation I found a few fuel related problems that corrected my problem. I did them all at once so I can't say for certain which was the biggest problem, but I knew I had leaks and problems in multiple spots. I can now hit 5,600 RPM turning a 24P Raker on my 19' bassboat.
1) Float chambers - All 6 float chambers were warped and leaking at the gaskets. Also, I had fuel weeping out of the pressed in BB's. I bought all new float chambers, put JB Weld epoxy over the BB's on the new chambers, and transferred my jets from the old chambers to the new.
2) Fuel Pump - I had noticed for a long time the engine smoked excessively. I tried different oils with no success and finally I determined the over-oiling was due to poor fuel delivery. I could have installed a fuel side diaphragm rebuild kit, but had concerns about trying to work with 25 year old plastic. I installed a new VRO Pump (yes, they are pricey) and now I just get 'normal' 2-stroke smoking.
3) VST - I had a small leak from the gasket at the top of my VST as well as the fuel filter. I replaced the tank gasket and installed a new filter and O-rings.
4) Carb Rebuild - While I was replacing float chambers I figured I should clean and rebuild the carbs while I had them off. I also found the O-rings on the fuel rails were leaking so I replaced them at the same time.
5) Primer - When using the primer to fog my engine I had noticed fuel leaked around the red knob when I turned it. I installed a kit with new O-rings and top gaskets to eliminate those leaks.
6) Fuel Hoses - When I did this work in '22, my boat was 25 years old. I figured it was worth the effort to replace all the old fuel hoses and primer bulb to eliminate the possibility of weak, collapsing lines. Additionally, my boat has dual fuel tanks with a selector switch and that knob had become very difficult to turn. I replaced that as well. This was probably overkill, but it let me check off a possible point of restriction.
All told I had about $1,000 in parts and hoses. That's a big chunk of change, but on a 25 year old engine that had only ever had spark plugs replaced I don't consider it too much. Ethanol fuels and repeated heat/cool cycles take their toll on plastic. I figured it was time to refresh those components and it solved my problem.
