2000 x 172 120k miles service history up to 82k engine ticks over fine smoothly on start up but once you have taken it out for a blast and listen to it, it sounds like a diesel there is something more than rattling in the head metal on metal i have had the screwdriver to my ear but cannot define the source also as soon as you take it over 3000 revs the noise goes away there is no loss in power at all it is still a rocket i have had an engine flush with recommended oil and had numerous mechanics listen to it they have said that is possibly timed up a notch out or something there not trying to get me to do the work so i presume this is an honest opinion could it be something as simple as this or something more jubious