Rob,
Welcome to the Forum
You will find a lot of help here.
Usual protocol wants you to post some images of your 911.
Add some good engine images.
Post the engine number (green arrow) and the engine type number (red arrow). (Ignore yellow)
If you have A/C, you may need a flashlight and mirror.
Once you are certain of the engine type, we can help diagnose the running issue.
Does the engine run properly above and below this rpm?
Is it more pronounced with part throttle or full throttle?
Is the hesitation and ‘sputtering’ when attempting to smoothly accelerate up through the rpm?
or
Is the hesitation and ‘sputtering’ when attempting to suddenly accelerate from some speed?
Does anything else happen (like the tach act up)?
What is the history of your car and engine?
Rebuilds, tune-ups, compression/cylinder leak measurements, service, etc.?
Best,
Grady