Keep your eyes peeled for an RB TM01 pipe. They come as silencer only and won't cost the earth. It was designed to bring the best out of the RB TM728 engine. I have one on the Savage and I am using it with the K4.6 engine. Seems to be pretty good so far. There is also a new pipe from Hong Nor, I think it is called the 094. The only problem with that one is that it comes as pipe and manifold, so you would be paying extra for something useless.