It might be worth cleaning the filters too. These are accessible by removing the rectangular plate on the bottom of the OD, and then unscrewing the correct plug. Read the book! You can make up the special tool with 2 prongs. That and an oil change may do the trick. Mine is much improved. If you know the OD is a bit sluggish don't let it slip - change when you are not applying torque, and wait for the revs to change before stepping on the gas. You may well get many miles out of a tired unit with careful use.