Odd injector sound

Truck has recently started what sounds like an odd injector tick. Almost sounds like an exhaust leak tick but doesn't get louder with throttle or anything. Almost sounds 'springy' if that makes sense. Seems to be prevelant from 1400-17/800 rpms then goes away. When it first started it seemed like it'd go away once the truck war,ed up a bit. All 8 buzz equally loud, 5 fails contribution test but the sound is on the drivers side and not the passengers side. Injectors have about 90k on them I think