found one on street unit forum, they say 50:50 and recomment 100 % rec. with the cap to have a space of 0.63 cm's and to wind it in 1/5 turn till boost hold and any back fire stops.

I got it due to a) not likeing a plastic one b) got FMIC installed. the noise VIA the SRI is enough as it's really loud.

StreetUnitForum.com