Confirmed that I am able to run higher speeds with the guides than I did before them. I'd have to look back at my posts or break out the tach to get an exact number...but I do know it's a few k faster than I used to be able to run. Pretty sure I'm using the .025 wire and .032 mig tip as well.
But I also changed to a longer needle, changed from the crank to the flywheel, went with a lower kv motor, and changed from the air needle to mig tip at the same time. So...hard to say just which made the biggest difference. I wish I had the time to test the changes individually but not being retired, having a young child, and way more projects than I have time for already that's just not going to happen
I do also use the cotton ball oiler above the mig tip and I do notice a difference in cut quality and heat when I forget to oil it after it's had a lot of use or sat for a few weeks. So that really does seem to help.
I also know that on my previous cutter the mig tip did run hotter than the air needle guide when compared with all else being the same. But I prefer the mig because:
1) It lasts MUCH longer
2) the air needle can fail - some fail after very little use and some don't even last one use they're so cheaply made.
3) the mig tip doesn't need any special prep while the air needle needs to be trimmed.
4) You can solder on some heat sink fins if you're having heat issues with the MIG tip. (I've also considered chucking it up in my drill press as a poor mans lathe and using the cut off wheel in my dremel to cut some grooves in it turning it into it's own heat sink - but since I haven't had heat issues due to the other changes haven't had to resort to trying that or adding fins.)
I can think of a few reasons for the heat difference. The mig tip is a tighter fit (but I like that since it should give a more accurate cut), the copper of the mig tip may be a bit "stickier" giving more friction than the material the air needles are made out of. The air needles have way less mass so the can't hold much heat in while the mig tip's extra bulk can really hold the heat.