2010 CX-9 Suspected Engine Stumble??

I have a 2010 CX-9 3.7L engine
I have had past issues when accelerating to about the 45-50 MPH range and the vehicle would "shudder". I had the CV joints replaced and that cured some of the issue.
Now when you slowly accelerate through 30-40 MPH you will feel a "stumble" as if you were driving across speed bumps, It will not happen if you accelerate very fast though. I have changed plugs and coil packs, and their is no CEL on.
I asked my wife to put 93 fuel in and she said that it slightly felt better but it was still present. Not sure if it a motor, transmission, or drive train issue??
Any help would be greatly appreciated

Thank you
2009 cx-9
Update: this did fix my problem.

I have a 2009, 100k miles. Have had this problem for a week now. They diagnosed it as an oil pressure switch needing replaced & new spark plugs. I will report back if this does not fix the problem. Its costing $800
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08 CX-9 GT FWD
H. Blanchard, welcome to the forum.
If you have all wheel drive, I will direct you to the all wheel drive failure thread in this forum which has pages upon pages of posts.
Your transfer case (PTU) may be failing which most of the time requires a new transfer case and transaxle assembly.
I hope that's not the case for you but is most likely to be the issue. But again, hopefully not. Can't think of anything else.
I only use 89 once in a while to clear out some carbon build up which causes pinging upon cold accelleration, but this stumbling issue, other than spark plugs or coil packs, not sure what else would cause that.