Backfiring And Pipe Discolorization

I have the full HMF pipe with CB, and lid off. It did improve the power over the stock pipe and header by a few HPs. I do run it a lot with the quiet insert to keep the noise down around my private riding area, or when I don't really need every ounce of power.

I have had some issues with backfiring more than I think it should. It happens after I let off the throttle. It just happens a lot.

I also have discoloring on the header more than half way to the pipe. I know to the first bend is normal, but again, it is going too far for what I know.

Can any of you give me a basic idea as to where I might look into for getting it right? I do use the stock airfilter and I am in Chicago, so altitude is not the issue.

I don't know if I am lean, rich...I am no mechanic.

Thanks as always for your help.

Tom