[Dave at Pelican Parts]

All of the 2.0 liter cars should have D-jetronic FI. The idle spec for CO measurement was 3.0% for the D-jet cars up through 74. 2.5% is a little lean but should be doable; I think the spec for non-catalyst 75+ 914s was 1.5% (though I could be mixing that up with a different figure). Higher numbers generally indicate a richer mixture, while lower numbers generally indicate a leaner one.

How's the basic engine? Valves all adjusted to spec, good compression, and so on?

Check your fuel pressure. It should be 29 PSI any time the engine is running. Higher pressures will give you richer mixtures, and lower pressures should give you leaner mixtures.

Check and re-check your ignition system. A poorly-performing ignition can lead to incomplete combustion which will register as excess HC and CO. Incorrect timing can lead to high CO or high NOx, depending on which way you go. (And I don't remember which way is which.)

A very lean mixture could also lead to incomplete combustion and misfiring.

Check to see if your manifold pressure sensor is holding a vacuum. Pull a ~5" vacuum on it with a vacuum pump (e.g., MityVac) and see if it holds pressure for 5 minutes or more.

Check the resistance of the head temp sensor circuit. If it's more than a few hundred ohms when the engine is warmed up, the mixture will be too rich.

Air leaks, particularly near the heads, can cause weird running problems and quite possibly emissions problems.

Most 75-76 914s did not have catalysts, even though all of the ones for the US had the nasty roundy-round system that allowed for the cat. You should, if everything is in good working order, be able to pass that emissions test.

--DD