The European exhausts are the best tested on the dyno and at the track. The scalvini produced good power in the top end, and the engine needs to be tuned for this type of power, the pipe is thin and will get damaged easily , the damaged pipe will have a loss of power. Van Hasselt exhaust is specially designed for MX, best mid range power and easy to race , and the construction is good. the HGS has the best top end power out of all the pipes, but engine must be tuned to suit this for the rider. All pipes have more power than the stock pipe. USA pipes, euro pipes included. USA pipes crack alot. Euro pipes are stronger and make more power, but are not coated and rust easily. Most of the power increase comes form the pipe, not the silencer . The silencer does change the engine noise alot, but the dyno tests show no big power changes are made.