If it’s stuttering it’s back to the basics- air, fuel, fire. Y’all got an ODBII reader? MAF is very much an option, does it have any blowby?

No I’ve been meaning to buy a reader, just haven’t needed one yet. But I think that’s a good idea

Also, unless your regularly change your transmission fluid in a vehicle, do not change it. A good transmission specialist at a well known shop told me that years ago. You can actually could harm or destroy your transmission.