S4 and S6 leading spark plug locations affect on timing
 

This has been something that has bothered me for awhile. Mazda supposedly moved the leading plug for emissions purposes, but it doesn't matter much why it was moved. How much does this change affect ignition timing (leading and split)? Lowering the plug physically advances the timing, but does anyone know how many DEGREES apart the leading plugs are between series? I would think it would be wise to run less timing on an s6 housing compared to an s4, but not knowing how many degrees they are apart makes it more of a guestimation.

https://www.rx7club.com/2nd-generati...5-13bt-363431/

This is one of the few threads I've found this topic discussed and it was left at odds. does anyone else have any input on this topic? I personally find it hard to believe that it doesn't matter or affect anything.

It would only be a problem if you're trying to use an S5 tune/ecu on an S4 block or vice versa. Or a keg with mixed series housings.
Since the timing maps are locked in the ecu, it's unlikely to accidentally mix them due to the wiring differences.
Sure it wouldn't be running at full efficiency or a little advanced timing, but I'd doubt it would cause an NA or stockish TII to blow.
If it's a situation where you can actually do something about it (tunable ecu) then you just optimize the tune and pay a professional guesstimator tuner