FWIW I'll share my experience with a V-Force 4 set up on my NF4 RS125. This was an upgrade that was part of an engine re-build and tune by a great 2 stroke guy. I did not dyno the engine before and after the V-Force but the engine was unbelievebly better than before and I feel the V-Force was part of it. I did go back to standard reedblock for a while (reasons below) and I thought it lost a little bit in terms of power and driveability. If you search on USGPRU.net there are a lot of comments about the V-force (there may be some dyno comparisons, can't recall now). There seemed to be a strong consensus that it made significant improvements. Same on the RZ350 owners group website.

The problem I had was that the reeds would fray and chip at the end in an unbelievably short time which hurt performance considerably and made the bike very difficult to start. I suspect it was because the product is designed for the CR125 which operates at lower revs. The problem seems to have been solved by ordering reeds from Carbontech which have lasted longer, but maybe still not as long as stock reeds would last.