89 MR2 idle intermittently low

[m_schroeder]

OK, should be simple for those who really know this stuff. My MR2 drops down to very low idle conditions when it gets warm and under sometimes under load with the A/C running/engaged. But it is not always when A/C is engaged.

What parts should I be looking at that is allowing the idle to intermittently drop too low to start a breif shaking? Ignition is good, fuel delivery is good (not a super, but injected). When its cold, idle is solid, it takes at least 10 freeway miles to start this and a hot afternoon (easy when in Phoenix).