Todays fuel isn't helping anything! Several issues occur and it's best to just replace the carb complete. It's not that expensive. Aftermarket ones are available for 200$. Dual fuel or straight gas?? Either way the carbs are so worn out and it's usually the throttle shaft seals bad. IT's replacement time. Run the vac lines to the same ports. Possibly 4. Also there's gaskets needed on the intake. 3 total. Heat riser , and 2 sealing. Check intake throat for carbon buildup. Carbs are 98% set up to drop on and run.