Should see a few 360s & plenty of 66s along with both FL & GA 90s & possibly a couple of 86s. Several liners avoid Ipswich however going direct to/from Felixstowe via the Bacon Factory Curve.
They are but only between Norwich & Diss. Only chance you have is of a new unit being delivered from Dollands Moor but that has been happening early morning.
And do you happen to know what the greater anglia service operated from Norwich T.C. to Ipswich and back is? http://www.realtimetrains.co.uk/train/L28083/2019/01/31/advanced
That's a 90/DVT set by the looks of things. Not sure if it actually runs as a test trip if required or it's a tyre turning trip to Ilford that stables there for a bit.