A/F ratio problem ?
 

What does it mean if my autometer doesn't moving back and forward in close-loop.It's stay lean even I'd adjusted my fuel regulator to rich.

it sounds like you have the A/F gauge connected to the wrong wire.

But It had been working perfectly before. So I didn't connect to the wrong wire.

it will only move back and forth if the ecu is capable
of keeping it close to stoich, if you're a little bit richer or leaner
than the range of your O2 sensor, the ecu won't be able to do its
job at cruise because its outside its allowed trim values.
but i suspect you'd get a CEL if thats the case.
but then by your location, you probably dont have obd2 compliance,
so it could be the case.

See if you can find a local tuner, get a wide band hooked up
to your tail pipe and get some true readings, your O2 sensor
has a very limited range of operation.
if you can't, hook up a voltmeter and measure the voltage,
it should change just as your meter does.
whatever you do, dont use that meter to tune your car

bry

Ah, you didn't mention that it worked before. I thought you had just installed it.

Your o2 sensor could have died, your wiring connection could be faulty, or it could be changes you made to your fuel pressure, or some other component.

I would double check the gauge by reading the voltage at the o2 sensor. If you really are running that lean, you need to drive very carefully to your local tuning shop and have them fix your setup with a wide band o2 sensor as bry had suggested.