[yelcab1]

I am working on a relative's 87 carrera. The car has a slightly lumpy idle. So far, I have done:

1. valve adjustment
2. new spark plugs
3. new dizzy cap
4. new rotor
5. new 3-wire universal O2 sensor

The car will fire up just fine, runs real smooth for a few minutes, and then settle down to a slightly lumpy idle (meaning with some vibration).

No obvious air leaks (I know they can be non-obvious)
I will want to clean the Idle Valve
The airbox has a small crack BEFORE the MAF meter so that should not affect idle

I still have a few other ideas to check but I like some recommendations as well.

The question is what does the ECU do during the first couple of minutes after starting that is different from a few minutes later?