Mahle 92mm RSR P/C's 10.4:1 using RSR heads (early version with CE ring grooves). Thankfully, the late versions do not have them anymore. With 2.4 or 2.7 heads, your CR is around 11.2-11.3 and thats why it detonated, especially using single-ignition.
Headers kinda look like Bursch ones.