I replyed to one "thumbs down" comments on Grose-jets last week with an Amen.
My specific experience with these jets on twin SU HIF's on a 1973 MGB was not
good. I installed them the first time I was into the SU's and found them to
prone to sticking open, even with running a Fram G-2 paper filter.
I had the car for about two years, driving it everyday, with standard Viton
tips then switched to the Grose-Jets. After a couple of weeks I began to
have flooding problems. I fianally ended up replacing them with new standard
jets. That was about six yers ago and I haven't had any flooding problems
since. The car has always been a daily driver.
In my opinion, the soft Viton tip of a standard jet is most effective and
also MOST forgiving of anything that manages to get through to them.