My Altima 1998 has bad idle after started

[darkmaxx1]

During winter (December), it was a pain to start (it even killed my battery )
So I went to dealer (March) to clean throttle body and injectors.

Since then, it seems to start up more faster (maybe the temps are warmer)

But, the problem is when it has been started, the revs goes to 2k rpm and goes back to 1k rpm. Then it goes to 2k rpm and goes back to 1k rpm again.
At the end, it goes slowly to 2k rpm and goes back to normal.

Sometimes, it stucks at 2k (or 3k when really cold) rpm until I put it on reverse or drive.

I suspect there's a leak at the intake manifold gasket as the altimas have that problem.

What would cause this problem?
Thanks! ^^

[SentraSE-R]

A leak in the intake manifold gasket would cause that problem.

[darkmaxx1]

I got replaced the throttle body and the ECU.

It fixed the idle problem.