Original symptoms:
1) Stuttering idle
2) Engine shut down approaching stops
3) Low gas mileage
4) Hesitating engine

Attempt to fix:
1) Lucal oil treatment + high octane gas (went through tank)
2) Junkyard IAC valve - cleaned with acetone, ethanol
3) IAC relearn - although CEL never blinks for me (why?)
4) Cleaned TB, MAF
5) New air filter

Current symptoms:
1) No CEL
2) Intermittent hesitation in 1st,2nd gear
3) Hasnt died coming to a stop...yet
4) Cold engine RPM @ 1500
5) Warm enging RPM breathing between 700-900 rpm (@~0.5Hz)
6) When coming to a stop (warm engine) RPM @ 1100 for 2-5s, then down to 700-900.

Plan this weekend:
1) Clean EGR
2) Seafoam
3) New NGK plugs

Other observations
Very sensitive to airbox (this one) - rpm <500 and barely moves when removed.

Questions
1) Is my approach correct? Suggestions please!
2) Is this going to cost me lot in the future? College student budget here
3) Is the car reliable to drive on the highway? Hasnt shown power loss/hesitation, etc @ high speeds (3rd,4th,5th gear)

thank you!

Edit: I have done a thorough search here and suggestions are fairly well grouped in favor of (in order of frequency of suggestion for 4th, 5th gen):
1) Stuff i've done already
2) MAF sensor
3) Fuel Injectors
4) Timing
Coil packs (only for 99s)

 

It looks like you are doing your research. I like the NGK V-Power copper plugs. While they last roughly 25,000 miles, V-Power coppers are advertised to work well with older coils. Look for a blackened or fuel wet plug (as compared to others) that could indicate a leaking injector o-ring.

I try to keep a spare MAF in my workshop that I've purchased at a junk yard and tested for future use.

I would clean the EGR (w/tube) and see how it goes after changing and inspecting the plugs.

 

You're on the right trail. It's either MAF, injectors, or coilpack related IMO. Based on your observations, I'd start with another OEM MAF (no ebay generic MAF's) from the jy or from someone here in the classifieds.

 

I'm going through the same thing with my 96 SE. Ran injector cleaner; replaced fuel filter, cleaned MAF sensor. I would have days where everything seemed fine, then the choppy idle & stumbling on acceleration would come back. After a couple weeks I had a CEL pop - cylinder 2 misfire. Replaced coilpack and the misfire cleared up. I still had some random idle issues so I decided to pull the UIM and replace the valve cover gaskets and manifold gasket, as they were all 270k miles old! Project on hold for a bit after shearing off a rear valve cover bolt . Did you ever solve your issue?

 

I'd wager it's the MAF sensor also. Mine failed at 220k, I tried to clean it, it helped for 2 weeks, then the symptoms came back. I was getting the P0100 code but I hear they don't always trigger a code.