I thought i had a black bushing in it but it was rusty, i should have took it out and made sure. Apparently it came with the blue 21 degree bushing installed according to the MSD website so i'll take it back out and install the black bushing (18 deg) and shoot for 21 deg initial, it seemed to like that the best but it gave me too much total with the blue bushing and i got just a bit of detonation.