Without any check engine light to provide error codes then you just need to do the basics, and if that means paying people for labor time/expertise then that’s what you have to do.
You do need a good, locally owned, independent mechanic - someone who specializes in diagnosing and fixing car problems - rather than a national chain store that mostly offers pre-set “menus” of services rather than expertise.
You need to:
- Have spark plugs & wires inspected & replaced if necessary
- Have it checked for vacuum leaks - for which knowledge of using a vacuum gauge would be helpful.
- Have the fuel pressure checked, including under load
- Have your MAF sensor cleaned (easy to do yourself)
- Clean the idle air control valve (might be easy to do yourself).
- The EGR thing is also easy to do, and yes, if you pull the vacuum line from the EGR and have no further troubles, then it tells you that it is an EGR system problem.
I’m sure others might add to that list. Its all just very basic testing/maintenance stuff.