here's the situation:

everything was running well until a problem with the clutch pedal (body ripped at the pedals).
I used that 'opportunity' to do some overdue maintenance.

now, when the car idles, I can hear what I think is knocking every couple second or so; it sound like 'clank' and the idle is perturbed.
When I give a tiny bit of gas: no problem at all. Even 200 rpm higher is fine.

The scanner reports no problem, nothing on the knock sensor, the O2 readings are fine although super rich (108 blm, in closed loop). Even though I re-did the fuel tables when the engine was redone, the idle always sucked. It does it both in closed and open loop.

what is different:
- one new plug wire (stock wire, all the others are the old Taylor)
- new set of spark plugs (NGK TR55-IX), gapped at 0.45
- new header gaskets
- new O2 sensor wires (got burnt before too)
- EGR block off plate (replacing the cut'n'bent old EGR tube)
the rest of the fixes is irrelevant to the engine (new battery, new AC condenser, etc)

questions:
- if I mixed up spark plug wires, could it do that? (I'm going to go verify them one by one to be sure)
- if I created a leak at the EGR spot, could it do that? (if so, how to troubleshoot?)
- it could also be some unburnt fuel, I heard a few detonations in the exhaust; why would it do that now with no real changes to the configuration?
- if this is not one of these three: what should I look into?

I can't drive the car yet, the seats are not even in :S, so I can only idle and rev in the driveway... On top of that the laptop with the tools, tune and cable are in storage on the other side of the planet (literally)

 

I am such a moron....

I inverted spark plug cables....

it works beautifully now