I changed slip-ons on my bike. It's a '98 frame with a J-code engine. I took off a D & D than was in pretty rough shape and replaced it with what I thought was the same D & D. Turns out the new replacement was about 4 inches shorter. And now I'm getting a little bit of power loss at low rpms through 1st gear/early 2nd gear. Still screams on the top end. Any thoughts? Maybe shim the carbs?