I put v & h straight shots on my new fxstb. I've had these pipes on 3 previous bikes. The last bike, I started to notice some discoloration on the top pipe right above where the bottom pipe ends, after about 4,000 miles. On my new bike, there's more discoloration, at the exact same spot, after only about 175 miles. I'm sure it's not the air fuel mixture. I think it's just the heat from the lower pipe exhasut. However, has anyone else had this problem?