Your downstream O2 sensor isn't going crazy.

It's quite sane actually.

Without a catalytic converter it's reading the computer switching the fuel mixture from slightly rich to slightly lean.

The computer wants to maintain a 14.7:1 air:fuel mixture (stoichiometric mixture).

That's represented as 0.45 volts on an O2 sensor. The voltage operating range of the O2 sensor is 0.1 volts to 0.9 volts. (0.1V being lean, 0.9V being rich and like I said, 0.45V being stoichiometric.

The computer quickly switches the mixture slightly above and below stoichiometric in its fuel control strategy and that's what you're seeing on that downstream O2 sensor voltage. (It's acting like a downstream O2 sensor that's on a vehicle with a P0420 code because of non-functioning catalytic converter).

So even with those high LTFTs it looks like your computer is still able to maintain air:fuel stoichiometry.

As long as you don't have any exhaust leaks, having no catalytic converter shouldn't affect what the upstream O2 sensor is seeing and yours is seeing a lean air:fuel mixture. The computer is adding fuel as seen in your positive LTFT to bring the mixture back to 14.7:1

You say yours gets worse at higher rpms, raising up to +22%.

If this were a vacuum leak you'd expect it to get better at increased rpms.

1st inspect your spark plugs. Incomplete combustion from subtle misfires will leave higher levels of O2 in the exhaust and the upstream O2 sensor will pick that up and the computer will interpret that as a lean condition and add fuel. So even a cylinder that's running rich will be interpreted as running lean once it starts misfiring.

Make sure none of the plugs look like they're in a cylinder that's running rich or lean. Lean could be caused by a slightly clogged fuel injector. Rich by an injector that's leaking.

  Then check your fuel pressure to make sure it's in spec and you don't have a clogged external fuel filter (if it has one) or a failing fuel pump

Depends where you live.  Check out the laws in your state.  The LTFT numbers could be because there is less back pressure in the exhaust system without a CAT.

I live in Poland so there are no laws about it, your car just needs to run right and thats it. I changed spark plugs at 159k miles and now I have 180k miles. I will check the spark plugs at my nearest occasion. Thanks for help. I was just thinking will it run better if I put new catalytic converter ??

I put new WVE brass distributor and rotor. Old distributor was aluminium and was a bit corroded and used. I put new spark plug wires BBC laser mag wires - low resistance ones (around 1200 Ohm on the whole length) There is no static on radio or any problems with the car so I think they are well insulated. We took out 2 spark plugs and they were looking very good. So any other idea why the Long term is changing so much ??