Lowest possible ignition timing and higher RPM to keep it stable and smooth, or lower rpm, higher idle ignition timing? Which do you prefer to shoot for? Which is better for emissions, gas mileage, etc? I ask this because on my 5.3 with a 214/220 cam, there is noticeable difference in idle quality with higher ignition timing at idle(20*), and I am able to get the RPM a tad lower vs running closer to stock idle timing (11*) but have to bump the RPM a bit by about 50-100rpms. The 20* of ignition timing has a noticeable smell to the exhaust running a small high flow cat, where as the stock idle timing seems to run pretty clean with a less noticeable smell.