I have a 96 disco 1 with 155k. It runs well, after the usual minor to medium cost repair about every month, except the new issue: a sound EXACTLY like a cricket chirp coming from (my best guess sticking my ear into the hood) the rear passenger side top or bottom of engine. It gets more intense in speed and volume the more throttle (regardless of speed) under load. If i am going 60 and let off the gas, the noise stops. It is loudest when accelerating and at a stop or coasting the noise disappears completely. It has nothing to do with any belt, tensioner, pulley or pulley bearing as those are all new from an earlier problem. I have seen a lot of people with this problem say it was the cmp or camshaft position sensor o ring and replacing this fixed theirs. I just put a brand new one on mine and excitedly put all my tools away to drive it and the SAME SOUND IS STILL THERE! The truck drives 100 percent fine, full power and everything just this loud embarrassing noise! what other part can this be?! i am stumped and would be eternally grateful for some input