1999 4runner RPMs goes up and down

Hey Guys,

I've been dealing with these issues lately:

1. When I leave my car running on idle the RPM goes up and down and it feels like it wants to die sometimes.

2. When driving the RPM also goes up and down, especially around 2000 RPM.

3. I noticed when I step on the gas pedal slowly the RPM goes down a little and then it goes up.
(I would expect that the RPM would go up right away when stepping on the gas pedal).

I was wondering if you guys could point me in the right direction.

Thank you!
Josef

It's 1999 4runner with 210k miles on it. It doesn't have a catalytic converter installed (I bought it like that - the plan is to add it eventually)

 

Check for vacuum leaks! Certainly sounds like characteristic of a BIG vacuum leak. No lean codes thrown?