Same ticking on my 2000 LX 470 w/ 65k miles. The Dealer originally said in the 60k service that both manifolds needed replacing to the tune of $4,000. After I started asking him what would happen if I allowed the ticking to continue he said it was only one of the manifolds and they could replace it for $2,800. I still said no - he said that the valve could suck oxygen in through the crack and your O2 sensor will give you an engine warning if it gets to bad. Anybody out there just let the baby tick - consequences? Alternatives to getting it fixed - no warrenty here!