IAC and idle problems

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Hi

I have a 95 LHS and service engine light show code #25 at one day.
I changed the Idle Air control valve ( try to fix an old one first which was useless) and
now i have a new problem.
At first the new valve kept idle speed really high, approx 2500rpm. I let the engine warm up at the normal level and shut it down after that. Idle lowered a little bit, now 1500-1800 rpm.
I checked the installation guide and there is two different reset options. First is to let engine run 1 min (at normal temp) and shut it down like I did. The other one is to drive a car above 40mph and computer reset the valve automatically.
Okay. Just to drive above 40 mph (not so fun here in Finland where we got a good snowstorm two days ago and the car with 1800rpm idle, left leg pushing the brake almost all the time )
It helps a little bit anyway. Now the idle is 1200 rpm, but it's still too high.
I understand that 900 rpm is properly and here comes the question

How can I reset the pcm and/or valve? Has anybody had this kind of problem?

I must check the wires and connections if there is some shortcuts