So had the van out today for a run round & fill with E5 for the winter. It was running rough just off idle but seemed ok if I booted it. Idle was pretty decent so I discounted blocked idle jets. I couldn’t pin point it to any particular cylinder by disconnecting plug leads. There was an occasional backfire so i presumed it was running weak on one cylinder. Thought i had better check with the snail & found one bank was pulling more than the other. Not a massive difference but enough to cause rough running. Evened them up & now running smoothly. Hope this may help others with twin carbs that are getting these symptoms.
