Hi, Gil, I've used true venturis from Randy Smith, Eric Rule, Byron Barker, and I think others...I like about .180 on my ST 60's, then
fine tune with filters. Funny, as long as I've been flying ST 60's, I still can't see a difference between the true venturis and the
standard restrictors. I do like Randy's NVA's, they seem to eliminate the problem of small air leaks at the NVA.