For anyone interested to read about air balancing vs fuel injector balancing vs richer mixtures. The Background on page 7 of this Fuel Injection Patent
is interesting reading.
It makes four key points:
--Rough running under lean conditions is caused by power imbalances between cylinders
--Air Imbalance is not the main cause of these power imbalances
--Fuel injector differences directly result in power imbalances.
--Fuel injector imbalances can be solved by carefully matching injectors, or by running mixtures richer than stoichiometric (14.7:1 AFR)
The Wideband O2 project has taken the richer mixtures route so far. Although I'm considering getting a matched set of injectors and seeing how much the AFR can be pushed in the lean direction.