I imagine what you mean by "softer chambers". A lot of **** out there ...and I haven't seentit'tall...but not much softer than a 273 or mag before it's an open chamber again, that is in the wedges we're working with here. Dont run a hemi or a mag outside a stock 5.9 in my pickup. I ran 28 total timing max with 25 being ideal/smoother on pump 91...100 octane was more like 28-30 total in my 410, 9.9 comp 8.8 dynamic. Just enough octane the motor requires is all you need. Thats example is a lil outside the box and yes more octane can raise it up to the point of hurting performance. Before I forget to say this.. just build for the octane anymore if you trying go for it... focus there so you end up fkd and rattling when you put your foot into it....but really.. anymore octane than the tune requires is going to burn slower...and need "more timing" .Maybe that's what's happening, maybe not... but if the designed chamber is happy with around 30 degrees when all is right "stars aligned" ..then you wont need that much.
Stock stuff likes 35-36 ime, but we all know that motor is not a true blueprint piece and definitely not optimized for that chamber/head nor its potential even in stock as cast form.
