I've had my 2000 yukon XL (supercharged 6.0) for just over 5 months now and I've noticed I've got a lifter tick going on. The engine has 130k miles. The tick sometimes gets louder and sometimes gets softer at idle but its always there. I don't think it gets louder when I accelerate but I'm not 100 percent sure. I recently took it to my mechanic and he told me that he would have to take the heads off and replace the lifter. He told me this job could easily be over $3,000. Im going off to college soon and cant afford that so I told him I would sleep on it. After doing more research I've seen some guys using sea foam and other engine cleaning products but having limited success. (I also don't want to try an engine flush as I've heard some pretty bad things about them.) Ive seen a lot of guys replacing the O ring gasket on the oil pickup and that has made me think about how sometimes (only at idle) the oil pressure fluctuates and twitches pretty often. Could this be the problem I'm having? Could replacing that gasket make the lifter tick go away? The only reason I think this couldn't be the case is, as soon as I start to accelerate the oil pressure holds steady and doesn't budge. I also get pretty good oil pressure at idle. It fluctuates around 40 and 45 psi but like i mentioned before, it does jump around a bit.