These are sort of a weird mod. Some folks they work great, some they don't. I would say, as Phil suggested, not to bother at all unless you can feel a slump in the mid range. If they don't help, you can always sell them here to someone else. Not a big risk of $14.
I am running the Thruxton needles now (not recommended at all unless you have the big bore by the way) but ran the TBS needles before. My seat of the pants felt good with them so i sold my TBS when I was in Georgia. But since then, my dealer had a sale so I got another pair of the tBS to try when I get around to the dyno again. I will leave in the set that works the best.
