It shouldn't mess up the tune at all, unless the valves are so far out of adjustment that they aren't operating properly. You'd know it if that was the case. I wouldn't worry too much about the one valve, I don't think an engine with that low mileage is in any danger and I think it's probably just alittle noise that can be fixed at your leisure. Ask the guys at Abacus when you go to get tuned, and if they think it's OK to put on a dyno, it's probably fine.