Tuning Issues
If you have a very long duration cam in your motor, and it idles poorly, you might be able to get it to idle better through careful tuning with MegaSquirt. Often a rough idle may be caused by lean air/fuel ratios. This is really is more of a cam issue than a fueling issue. The exhaust valve is held open later into the intake stroke and the intake opens earlier near the end of the exhaust stroke. At low speeds and relatively high intake vacuum you get more exhaust contamination of the fresh air/fuel charge. As you get more contamination of the air/fuel charge you typically need a richer mixture to get it to ignite and burn properly.
This means you probably cannot run a stoichiometric [chemically correct] mixture of 14.7:1 with your long duration cam. You need to run richer. So you tune your idle by ear rather than with a narrow band EGO [oxygen] sensor. And make sure you are not allowing EGO correction at idle if you have a rowdy cam! It will be trying to “correct” your mixture back to a lousy idle. If your engine will not idle well at stoichiometric mixtures, set the EGO Active Above RPM to a few hundred RPM above your idle speed. This will ensure that MegaSquirt does not try to lean the mixture back to stoichiometric to compensate for your adjustments.Remember that O2 sensors give wrong readings on a missfiring engine, big cams drive O2's nuts at idle too, so dont rely on their readings at idle.
Another tip you can try if you have a large overlap cam is to pinch off the MAP hose slightly while the engine is idling, and see if the idle quality improves. If so, then try a restriction in the MAP vacuum line. This has the effect of damping the vacuum pulses that the MAP sensor sees. Start with a ~0.040" (1.0mm) hole in the line. You may have to experiment with restrictor sizes to see what works best for your system.