I've had issues with my previous XJ with this topic. Initially, i changed the o-rings in the fuel rail, and noticed a decrease in leaking, but it still leaked. Upon further inspection, i noticed at the front of the fuel rail there is a fuel pressure regulator, that has a vacuum line attached to it. I solved my problem when i replaced that vacuum line, it was plugged from something and not allowing the regulator to recieve any vacuum.
I'm not sure about the cleaning part... know there are a lot of products on the markey, but not certain if any are really worth buying.
My e-mail is Jeeep_man@yahoo.com... i don't check the one that this forum is attached to, and it will not let me change to a Yahoo e-mail.