Have you been able to address sticky lifter without surgery?
 

I have a sticky lifter(s). It surfaced in a noticeable way rather abruptly at the end of summer. During a $2,000 AC repair no less... The AC I never ever use. The engine sounded like an Italian tractor. We did the flush, run cleaning additive, put in fresh oil thing. Fairly quiet with a steady idle once again! After a long drive I couldn't hear the ticking at all. The plan was to dump this oil at about 3K miles. It's currently at 1,500 (I think 102K total). But since then the ambient temps have obviously dropped. I was considered it would sound and run terribly once it started getting really cold. I'ts not that yet, but I am getting that feint ticking again with a slightly uneven idle (well within one hash mark). On more moderate days of warmer temps, which we had a lot of before January rolled around, the ticking doesn't seem to be very noticeable at all especially after the oil is up to temp. Most passengers look at me like what the heck I'm obsessing over. I'm trying not to run the car so much which is easy since it's only a weekend car.

Have any of you been able to eliminate this issue altogether without having to remove the lifters? Would it hurt to run the cleaning agents after each (now shorter) oil change as part of a gradual process? I was amazed at how dramatic the change was after the initial cleaning.

The flush is a bad idea... The lifters are 24 miniature oil filters, they have one way for oil to get in, but the only way it can escape is round the piston.. Debris won't pass through the lifter, it lodges and stays there. The flush breaks more crud loose that ends up going straight to the lifters, as they are the end of the primary oil system.

If this is persistent, it probably isn't a lifter.. Its probably a failing cylinder. They sound exactly alike, same tone, rhythm and characteristics. Approach with great care, this bites shops and dealers all over the country with misdiagnoses.

Ha - JR beat me to it while I was (slowly) typing ....

I seem to remember a couple of threads from Raby suggesting that the lifters can fill up with gunk (which can't escape due to no oil exit arrangement) and they don't respond well to detergent flushes. I'm pretty certain that he modifies standard lifters in his rebuilt engines - what the mods are he wont say....
Are you sure its lifters? why would cold(er) weather make any difference, especially of you are using the correct 0W40 or 5W40 oil grade?
Could it be the dreaded bore wear "tapping" noise that affects the bigger capacity M96 engines on cylinders 5 & 6 - what is you oil consumption like?
I'd try new synthetic oil and see if the noise reduces.

Thanks. I passed on doing the lifter job initially. In the back of my mind were all the other things that can fail on these engines once it crosses 100K miles. Didn't make sense to only do the lifters. Either leave it alone or tear it down was my thinking.
I guess there's no getting the gunk out once they're in the lifters. Its just a matter of not creating more gunk by sticking to shorter oil changes and see what the M96 gods do to me for abandoning my twice a year oil changes in favor of longer stints on higher quality oil.
Moral of the story, twice a year minimum no matter what mileage or oil used.

Oil consumption is not an issue. I check it a bit too often some would say. That damn digital read out is so incredibly unrealiable that I've become paranoid. I say cold weather because if it is the lifters I would assume the gunk gets "chunkier" on cold start up causing them to stick easier.
My oil was like this: Mobile 1 0W40 for the first 50K miles or so. Then I went to Castrol Edge 5W40 for the next 40K miles. Motul Xcess 5W40 for the last two oil changes over 10-12K miles. Problem is it took a lot longer to hit that mileage while on the Motul. I definitely should have had four oil changes in there instead of just two in that time. I've never driven the car on short trips really, and drive year round, never less than 8K miles a year so. But contamination from oil sitting too long has always been in the back of my head.

You may also have a cam lobe or lifter that is wearing. Pay attention to the #1 cylinder, inboard intake lifter/ cam lobe. Listen there and tell me what you find with volume and intensity with a stethoscope on that part of the cam cover with the engine idling, warmed up.

If its louder there, I know what the problem is. Boxster engines eat that cam lobe and that lifter.

The debris in the lifters...hate to say dirt through air cleaner , or carbon bits from combustion chamber. I doubt if rancid oil contributes , but it has been suggested as culprit in the IMS failure as corrosion?