I ended up selling off the truck for a 10k profit and have a 4Runner TRD Off Road now. But it held up just fine for the 3 or so weeks I drove it after applying the grease. I did get under the hood and sprayed it one more time after my post for good measure, I jammed the boot back against the firewall and applied a bunch before letting go.... but the obnoxious creaking hadn't come back. The service guy agreed with my idea that it was the boot but didn't offer a fix since they had new trucks on the lot that creaked also. He lives around town, if I see him I plan to pass on the info.