They definately make them (see here).

I've run them before, the dual stage ones i got do look very different, seem to work no better (or worse) than standard though.
I didn't dyno them though, just seat of the pants stuff.

Carbon (Tyga) ones seemed to crispen the throttle up a bit and add a tad more zip but I did go to the HRC style stuffer at the same time so that may not be totally down to the reed alone.

Also I lost one of the (thin reed material) Tyga reed spacers and am running the thicker (metal) Boysen ones in their place, that too could mean my results are different.
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