"Whitepaper", or snowjob? If condensation and/or tracking in the cap is the culprit, cleaning & drying should provide at least a temporary remission.
A K-jet system left unused for seven years will also exhibit the symptoms being experienced by the OP. All the cold-start provisions will provide sufficient richness for an initial start, but partial clogging of metering valves and nozzles may cause a lean condition when warm.