I was cleaning the carburetor on my 2000 YZ426 when I discovered that the AP diaphragm was torn. I'm obviously going to replace it but when I go to the parts fiche there are 4 different part numbers for "DIAPHRAGM ASSY AP", and the prices range from $15-$24 at the TT store. 31 DIAPHRAGM ASSY AP(5JG1) 5JG-14940-05-00 1 $21.43 $19.29 31 DIAPHRAGM ASSY AP(5JG1) 5JG-14940-17-00 1 $16.98 $15.28 31 DIAPHRAGM ASSY STD(5JG1) 5JG-14940-18-00 1 $26.68 $24.01 31 DIAPHRAGM ASSY AP(5JG1) 5JG-14940-19-00 1 $26.68 $24.01 My question is: Which one do I get? What are the differences? What is stock on the bike? Right now, all the jetting is stock and I'll be doing the BK mod before I put the bike back together. Any advice is appreciated!!