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Well I was hoping to keep this to a general tuning thread. I know every engine combination is going to behave differently. For the sake of arguement let take two engine combinations.

First one stock 9.5:1 with motronic fuel injection. Perhaps first hand information can be provided by scarceller as I know he can proprgam his own stock system.

Second senerio hot-rod 3.4 with DC21 cams 10.5:1 headers full flow exhaust 46mm PMO ITBs, twin plug and full aftermarket engine management

This should about cover anything except turbos as most will fall somewhere in between or both are common.

Mine happens to be in the later category. It has been found by most that in senerio 2 of the hot-rod that an idle mixture leaner than 13.5 tends to cause a stumble coming off idle. There is alot of throttle plate opening at once. It has also been suggested that in the stock system you can go leaner and still have adequate acceleration characteristics. I am open to running leaner at cruise but attempts at idle don't work even when using acceleration enrichments. It just stalls then goes really rich. Cruise is still a mystery to me and is generally not discussed much. Lots of info on idle and WOT.

I have read that not having enough timing advance at idle will cause headers to get really hot. The initial programming of my unit had an idle advance of 12* btdc and I have read where others use that setting. I have also read the stock setting of 0* +- 5* so again conflicting information. Is one good for stock and one good for headers. I agree no knock at idle but in theory you could probably get knock at cruise on single plug when pulling a hill. The twin plug pretty much takes knock out of the equation and it becomes about how the engine runs.

If knock is not the problem with running an engine lean then what is the lean killer everyone talks about. I will assume super high head temps. What does 16 or 17:1 do to head temps during cruise. I don't have a true head temp (spark plug ring) I only have the factory cylinder temp and it does not appear on my system to work well under high load conditions.