If you mean the Breckland one, that's been a round for some time.
They used to carry on to Colchester or Liverpool St.
For a few years, yes. But they changed their mind. Although it
appears they still stable them in Colchester because the first/last
trains work there rather than Ipswich.
And of course it makes Liverpool St-Ipswich 'all electric' again. I
expect these changes were done when some extra EMUs arrived (probably
321's cascaded from London Midland) a couple of years ago.
That as well. The idea with the original eight 170s was to provide direct
trains from non-electrified Anglia destinations like Lowestoft.