These mufflers DO help with power, but there is a price if you are not careful, because they have no baffles, they generate less backpressure and therefore less tank pressure. You might run into problems because of this if your tank is long (or even not).

I had a Tower .46 that would die every time I accelerated vertically (i.e. loop) and after 3 weeks I found out the muffler was the culprit, an O.S. muffler fixed my problem at the cost of much of my power