Just a couple of things for you to consider. First, though AI rebuilt the carb not long ago that won't eliminate the possibility of potential problems arising. I've never seen a 3w not idle consistently when dialed in properly. My 157cs is headed into her sixth season without the needles ever being touched. I can only use this and my 170 as examples. They are the two dubs with the most time on them. However, the new 106cs, the 212cs and the 70 twin are still new enough (time wise speaking) and still breaking in. Most times I have found that when an engine is broken in and running consistently well then all of a sudden changes, something is amiss. Servo gear slop, worn or failing throttle linkage, weak ignition battery, dirty carb screen, fouled or worn plugs, worn or chipped reeds will all cause this. That said, there is something else I would consider. And for me it sticks out more so than anything else. Air leaks will most definately cause this issue. Basically if you are needing to bump up the trim or set slightly higher on the idle setting to keep it running, you're in essence giving it a placebo or band aid. I am curious if your reed block, reed housing or any other part of the carb ingestion system is the original style phelonic material. They have been known to warp over time and hence the 4 bolts that affix them to the engine become loose. Thereby allowing an air leak around the sealing surfaces. This is the biggest reason I updated all my engines to the all aluminum upgrades and new gaskets throughout. Add to that, most recently I discovered leaking cylinder gaskets on another engine. Not any of my 3w's. I disassembled the engine, cleaned all the surfaces and resealed all the gaskets. Needless to say that BE62 runs like a clock. Another example of what once was but suddenly changed. My sons DLE 222 sat idle for a while before he completed some changes to his big Edge. Upon restarting it, we noticed it just was not running like it used to. Needles were all wonky, didn't idle correctly, and had moments of "phasing" in the air. What we discovered was his gaskets had dried out, then started leaking. After all new gaskets including cylinder gaskets and a full set of new reeds, the beast 222 is back to her usual (and even better) normal self.
But back to your 106. I would want to know what exactly caused a change in the parameters. As we all know, typically things don't fix themselves, it only continues to get worse. I've never used an idle up as Snoops suggested. Lots of guys do it and I totally respect that. But my thought is this. If my engine is not reliable and dependable at any setting or at any attitude whether flying or running on the ground, then I simply will not fly the plane until I know it is right.
If I were to offer a suggestion, even though it seemed to run fine today... I think I would investigate everything and look for a cause. The aluminum upgrades for the 106 are not terribly expensive as is neither is a new set of reeds. But well worth the investment.
Earlier this year I updated the 170 and slipped in a new set of reeds. I discovered they were leaking. The engine still ran good but I had noticed it was a little rich on idle. Same with the 157. The 170 is honestly a brute force to be reckoned with now.
I don't mean to suggest that any number of these conditions are the culprit of your recently changed idle settings. Merely a few things to consider and look at.
The 3w 106 is quite the beasty little engine with a reliability rating unmatched by most engines of the same or like size.
I hope some or all of this information is useful. I'm a very devote 3w guy. Primarily because they are strong. But mostly because they are so danged reliable. At any throttle setting. Always remember, if a motor does not run properly, (especially one that previously did) there is a reason.