the other day after topping up with fuel from a very empty tank, i was driving along and noticed a faint ticking sound, not noticable when idling or when reving the engine, but when you get upto around 50kph, or if you put your foot hard on the brake and put the engine under load (like your about to launch it) it starts, it sounds as though its only changing pace slighty eg, when im going 100kph it sounds only slightly faster then at 50kph, and even when i boot it the tic doesnt really match the rpm so i don't think its a lifter (but not discounting it completly).

oh yea a few more things that might help, its drinking more fuel now and it seems down on power + sometimes when it gets to around 3500rpm it will hesitate for a split second then continue.

also took it for a 2hr drive along the freeway after noticing the tic (middle of nowhere couldnt be helped) filling up with fuel + "booting it" did nothing to silence it, like the "bush" cure for a noisy lifter (worked for me 9times/10 in the past[top with oil + boot = free-er lifter])

could it have sucked some air into the lines (tank was very empty took 68ltrs [70ltr tank] to fill!) or it it something a litte more sinister.

ps i fkn HATE ticking noises in my car!!

sounds like pinging to me, try running 98 in it and see if it stops