Impreza Outback / 99 / 110,000 mi / manual / everything stock

First the car started jerking (due to misfire I guess) when
accelerating, especially pronounced at the at low RPMs of 2-nd and 3-rd
gear. Nothing weird on idle or rev-ing the engine without load. No lack
of power when it goes above 3000 RPM on the highway etc. In a couple of
days I almost learned how to accelerate carefully with a bit more gas
after each shift so you almost can't feel it.

Then the CEL turned on. Checked the code - P1130 - "Front oxygen sensor
circuit malfunction (open circuit)". Reset the error code and in a
while the generic P0302 - "Cylinder 2 Misfire Detected" appeared (no
P1130 though).

Searched the web and found a couple of postings where this combination
of symptoms - misfire/P1130 was due to bad fuel pump. Tried to compare
which one is harder - to change the pump or the sensor and the sensor
behind all those rusty bolts and under the car looked the worse one.

So changed the fuel pump and fuel filter. And nothing changed. Well may
be the jerking a little bit and with the new pump the CEL never came
off (guess some better fuel flow helped a bit).

Next thing, changed the O2 sensor. The store had the universal (and
cheaper) one in stock. Read the warnings about the universal sensors
but this was BOSCH and looked OK. The problem with it was that it had
three wires while the OEM had four. The booklet has a conversion table
and they claim the missing wire is the common so OK I'll buy that.

With the new sensor though I immediately get P1133 - "HO2S insufficient
switching" and whenever I turn it off with the scanner it comes again
in a couple of seconds. The misfire is much worse.

Any ideas? I know I messed up with the new sensor (as if the old one
was good) not sure how though. There is a slight chance the new sensor
was bad but this -
http://glasairproject.com/soobdocs/codediag/P1133.gif talks only about
bad connections. And I'm only 90% sure I connected it properly.

Running out of ideas... Except taking it to the dealer or buyng OEM
sensor or even putting the old one back (which I still suspect is the
faulty element). Or even worse - putting the old one back and going to
the dealer so they can cure the original symptoms.

Any help is highly appreciated...