Agreed LightSpeed but the S&S engine runs at 9.75:1 CR, so not wild for a normally aspirated engine and well within the range for 95 RON petrol. I use 98 RON most of the time, with a free flowing exhaust, and never have any problems with pinking. For the miles I do I like to put the best fuel and lubricants I can in my expensive X-Wedge, I want it to last a long time. Possibly the issue with the standard exhaust and pinking is due to the heat build up in the heads causing hot spots and pre-ignition?
