You don't say how long after eating the 8.9 result was. But for me it would be a definite no, the blood sugar level thay say is where possible complications are born is 7.8, so I try to keep below that as much as possible.
Plus it's above the 2mmol rise in 2hrs limit I set myself, generally I try to ensure my post meal number is back in the same range as my pre meal one. I will only consider a rise of 2 acceptable occasionally with something I enjoy.
Why do you want to introduce porridge back into your diet? If you think you need more fibre, there are less carby ways of getting it.
Another reason for me is the amount of insulin my poor pancreas would have to pump out to reduce that 8.9.
My whole diet is aimed at reducing the amount of insulin circulating, in order to improve my insulin resistance.
Eating something as carby as porridge would for me be counter productive.
Ps
No such thing as a stupid question