Since I moved to Suffolk 15 years ago, friends I have here have often spoken about the "Haughley Bends" on the old A45 (T) road. When this road was upgraded, they left in place the old road as a ghost road, used now by walkers and cyclists, it is a pleasant stroll.
You can park at this end of the abandoned stretch, and walk about 5km back into Stowmarket. Or cycle, if it takes your fancy.