My TT 61 Pro is at least 3 years old. I have no idea if it has an old or new carb.
When it was pretty new it was hard to start, had idling and transition problems, and the high speed needle was very touchy (a click or two either way and it wouldn't run). All of the "gurus" said it was too rich on the idle needle, loading up, etc. We (my brother and I) kept leaning it and several brands and types of plugs and I was about ready to toss it and buy an OS. One day we went to the field early, determined to fix it or toss it in the trash. We richened the low end a lot, probably a full turn, and started it. The high speed then needed major adjustment. We kept richening the low end and retuning the high end through several iterations. Now it starts easily, idles forever, and transitions pretty well. I've seen engines that have better transition, but I have full confidence that I can abort a landing after a long glide without fear of it quitting.