I'm curious as to what could be the cause. The bike is a '82 Kawasaki GPZ550. It has an MAC pipe on it which is aftermarket. When accelerating it pulls well initially but right at about 5400-5500 the bike doesn't pull as hard. When the revs get past 6500 it comes alive again and hauls all the way to redline which is about 9000rpm approximately.
Could a shop fix this? Will it be expencive?