2TR-FE 2.7L Hydraulic Lifter Issue?

The sad story: at 164k miles, I had a coolant bypass pipe rupture. Unfortunately, I did not heed the clue that I had no heat in the cabin, figured it was a blocked or failed core. No smell of burning coolant, and I did not notice the temp gauge moving up. Simultaneously, the check engine light shad come on and the earliest my shop could get the truck in was a week. No symptoms, no worries, probably a vacuum leak or O2 sensor or some such.
Two days prior to the service, the truck shut down from overheating.
The head did warp, so I had it fluxed and milled and reinstalled.
Here's my issue:
On that fateful drive, for the first time since owning the truck, I noticed a lifter tapping noise.
Now that the head has been serviced and reinstalled, the lifter noise is consistently present at certain RPM/load conditions.
Questions:
1. I have a good shop that I like to trust and they see no connection between the overheating and simultaneous sudden lifter noise. I would like a 2nd opinion.
2. Whether or not the overheating is causal, I suspect that one or more of the hydraulic lifters is at fault, since in a week of driving they have not settled in. Is that a good hypothesis?
3.If that is the case, can I solve it with an additive?
4. If not, can I locate just the one or more faulty lifters and a. remove and service, or b. remove and replace?

Thank you

There is a previous thread on identification of which i4 engines used mechanical and which used hydraulic lifters. the 2TR-FE has hydraulic lifters. I thought this merited a new thread.