93 Legacy engine hesitation when hot

My 93 legacy sedan LSi started to randomly hesitate at cruising speeds (not during acceleration or idle) last week. The engine will just drop RPMs for less than a second, then come back again. The problem is definitely worse after the car warms all the way up.
So far I have:
put in new spark plugs and wires,
changed the fuel filter,
changed the air filter,
cleaned the Mass Flow Sensor,
and changed the PCV valve
I am still having the problem. Any ideas on what to look at next? O2 sensor?
Thanks,
Eric
So far I have:
put in new spark plugs and wires,
changed the fuel filter,
changed the air filter,
cleaned the Mass Flow Sensor,
and changed the PCV valve
I am still having the problem. Any ideas on what to look at next? O2 sensor?
Thanks,
Eric
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Comments
How old is that ignition coil? I replaced mine and it fixed a hesitation issues on a 98 Forester.
I don't know how old the coil is, but I checked the resistance across it, and it still matches the specs..
Interesting about the gas cap - I kind of like the cap that is on there.. I'll have to see what is involved in replacing it - I'm assuming there are just a few screws..
After doing those changes, it has still been hesitating very randomly - sometimes not for days. I ran a 'fuel injector cleaner' in two tanks of gas recently, and I haven't had any hesitations in the past week. I know that stuff is supposed to be a joke, but is it possible the injectors are just fouled and the in-tank cleaners are working a little?
Thanks,
Eric