Fannie Mae and Freddie are apparently trying their best to keep up with the booming market in non-agency MBS, as recent data indicate the two companies have boosted their overall purchases significantly even though their share of total issuance is down slightly. According to data gathered by Inside MBS & ABS, $115.2 billion in non-agency MBS issued during the first five months of 2005 was carved up for purchase by the government-sponsored enterprises. That represents…