I am in the market for new exhaust and was wondering which would be better: 4", or 5". I am not interested in loud and will put a free flow type muffler on whichever one as to avoid the dreaded "drone" that I read so much about. I was looking at a 4" system from J. Jardine and posed the same question to them. They informed that with 5" I would lose some turbo spool up. Does that sound right? Any advice is much appreciated.