I have a TRX5 on my 350 but dont have enough seat time to give a fair review of it.
I always thought a pipe was a pipe till I went from my pro circuit(which I sold my FMF to buy) to a Sparks TT on my 275 and it made a world of difference. Not only did it have more power all around, it was smoother, easier and more fun to ride. Its funny, just by looking at them, the shape was barely different between the two, but you sure could tell a difference riding it.