Straight pipes will make it sound very raspy, really does not sound "right", not worthy of a BMW, don't do it. I tried it for ten minutes, sounded stupid and annoying and had the shop put the resonator back. I bought an Eisseman (spelling wrong I know) race exhaust and it sounds great, had the Dinan exhaust but wanted something racier and deeper sounding. Fits the X5, not annoyingly loud or raspy sounding. I have the Dinan exhaust available for best offer, am about to Ebay it. Someone sold theirs for $580, reasonable I think for mine also. It sounds much deeper and sportier than stock but not as much as the Eisseman Race exhaust but then, not as expensive.