gidoks

Before you go ahead to do all sorts of things, just first reset the EFI fuse in the fusebox. Pull it out for about 30 secs and put back with engine and all accessories off. Having cleaned the IACV its now freer and lighter thus reset would help the ECM recalculate the present condition.

Well ALL rules have exceptions and IMHO the 1MZFE of the 99/00 would be one for this rule. An engine as prone to sludge as this one should never be run on dino oil. I agree with you. I changed mine to synthetic oil, and sure saw some leaks underneath the sump. But that prompted me to loosen the sump and changed the gasket. In the process I found lots of metal debris in the sump and dark oil, though I just put in a new oil;cleaned everything and new synthetic oil.No qualms for months now.

You can check and change( if you haven't) the cabin a/c air filter and clean/service your a/c element.Dirty filter leads to dirty air and dirts on the a/c element thus reducing a/c efficiency.

What I did to solve that problem after searching in this forum was to raise the A/C setting. I raised mine to 75 degrees F and it stopped the noise. In other words, you reduce the load on the A/C preventing it from blasting at full fan speed.