my stft1 is reading -2.3 when evap is purging and after the purge has finished 0

What is your question?

my stft1 is reading -2.3 when evap is purging and remains between 0 and -2.3 after purge has completed! could this be a factor in why re-fuelling my car is a chore? takes about 10 minutes for half tank. kind regards graham