I have stock exhaust on my 2000 GT Looking to buy some flowmasters while looking around though i saw that they have series 30's now. I know that the 30's are single chamber and the 40's are dual chamber and my other stangs i have gone with 40's and i know that the 30's would be louder but is there a performance diffrence and is there a diffrent tone to them to the 40's because i like the clean sound of the 40's just seeing what you guys think. Thanks