Idle speed high! Help!

hi everyone. first time in here. found this forum when i was searching the web for my problem. wish somebody can help me.
my 97 rodeo 2wd 4cyl has idle problem. when i start it up, rpm goes to
2000rpm and goes up and down between 1500 and 2000. i put gear in 1st and it just runs without putting my foot on pedal(its manual trans)
does this for 30min and rpm just comes back to around 980 which is
normal. after shutting down engine and parked for awhile, when i try to
start it again, rpm stays low like 500 and sometime stalls if i dont give
some gas but normaly comes back to 980 after few seconds.
car runs fine when it starts with normal idle speed.
one time check engine came on, scanned, P05~
idle speed higher than expected..

dealer told me its my aftermarket cold air intake, so changed back to
oem but no luck. changed intake manifold gasket no luck. egr changed
a year ago. timing belt, warter pump changed 6month ago.

thought its MAF(mass air flow) sensor but this car doent have one.
suspecting O2 sensor or MAP, TPS(throttle position sensor)

i will be glad if anyone has advise or sugestion.
my GF dumped me last week for spending so much time trying to figure
out the problem.....I love rodeo more than anything like rest of you here.

thanks

i forgot to put my miles, its 75000
and i replaced Idle control valve also but no luck.

thanks

i will keep updating for someone whos having same problem.
i changed TPS(throttle position sensor) today, but no change.
while i was working i found a crack on my exit pipe right before
cat converter. it was leaking my smoke. i was wondering if it has
any affect on my O2 sensor located after cat converter.
thinkin smoke leaks out of that crack and O2 sensor thinks theres
not much of O2 coming out my engine and trys to put more air into it.

not sure if thats the cause but i will seal it off weld it. and replace
both front and back O2 sensor tommorow.

they were both $51 each from autozone, bosch brand.

also changin my IAC valve cuz my mechaninc doesnt want to trust
the one got from dealer real cheap.

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