Well I realise this post is quite old but I did come accross this quote in the service maual; "The volume of fuel injected is compensated when the feeding voltage of the battery is low." It was in the technical features section regarding the ECM. Whether that would be only at start or all the time i can't say, but it would appear that replacing the battery did help and this may have been part of the reason why. Before anyone goes there, yes when running the R/R should have a fairly stable voltage but electrons being what they are, you never know.