My friend has a DS650 with a Graydon Proline full system on it, and when he put it on, he said he had flames comming a foot out the back of the silencer! Has anyone else had this happen? Does this mean it is lean, or rich? He says it happened every time he let off the gas, and it idled down. It was followed by a Bang sound.

He might be selling his system to me, is it worth buying? I have a modded endcap, I think it's modded by biggerisbetter. Will the Graydon system be any louder than that, and if so, how can I quiet it down? Supertrapp disks? Quiet core?