HP Laser Printer 5Si Streaking

My printer has recently started leaving streaks on the top and bottom edges of the letter sized pages. The smudges are spaced 3 3/4 inches apart. The upper smudges are very narrow and about an inch and a half long. The lower smudges are a bit wider and show ridge marks, they are also about a inch and a half long. I've just ordered and replaced that parts of the maintenance kit (refurbished): the fuser, seperation rollers and transfer roller. This did not work, the smudges look exactly the same. Please help :)