Bonneville America Forums Forums Technical Forums Performance Mods Shimming Question

Here's my deal. I did the airbox cutout on the bottom, have 135 mains. My bike ran great until I desnorkeled it.Then my bike started to backfire on decel again when I desnorkeled it so I ordered some shims. I have 135 mains. I also have a K&N airfilter I was getting ready to mod and put in but am afraid to do it now. I pulled my needles out and there were two large brass shims already in place!! I went ahead and put in the 1.5mm shims my shop shipped to me. Did I f$%k up? Or do some models come with these big brass shims already in place? Please help......