Well, I removed the clip on the needle, set the float level, and changed the main jet to 130. Checked the coaster enrichment, all seemed good. It was oily inside a bit. haven’t checked the compression yet. I am running non-ethanol gas also.
To recap, I have the air box opened with the snorkel cut back (not removed) and 2 1” holes in the side of the air box, air screw 3 turns. I’ve done the Z1 mod; it sounds cool.
The ride after these changes...nothing improved. But it poured on me for a very wet ride!
Next step is to change the main jet down to 125, cover the air box holes and if needed, change the snorkel back to stock.
If I turn the air screw in, it will be pretty much back to original except for the Z1 mod...no going back there!
i appreciate the ideas and help.
Stay tuned

Ok... I didn't catch that you'd added holes to the airbox in addition to modifying the snorkel. I'd cover those holes and try it with the 130 jet. You should only need those extra holes open above about 10k ft altitude.

You already stated that you tried to change too many variables at once, which is always risky when dealing with carb tuning.

Easy way to check what effect the holes are having, without removing anything: put heavy duct tape over the 1" holes you cut in the air box.

Have you checked valve clearances? They were quite tight when I bought the XT in 2016.

Soon after getting my 2006 XT225 in 2016, I did the Z1 mod (1.75" hole), backed out the idle screw, and went to a 27.5 main jet. I did not adjust the needle, and I did not remove/modify the snorkle. Later, I cut a slot ~0.5" x 1.5" in the top of the air box, putting a piece of screen over it. Plug chops suggest it is jetted correctly. All my riding takes place between 1500 and 3000 feet elevation.

The old owner visited last fall, and said, "Wow, I can't believe this is the same bike." With a 16T countershaft sprocket, it easily holds 70mph, and I have seen 80 mph (indicated), but the chassis is not really stable above 75 mph.

[img]https://photos.app.goo.gl/2jLvuL2m13V51qTP9[/img]

Go for a high speed ride with a roll of duct tape. Block off a a small amount of air box opening, and keep blocking a little more each WOT run. Is the problem getting better or worse. This will tell you if your problem is too lean or to rich.

Thanks for the follow ups. I’ve been remiss in giving updates but here’s what’s happened:
Taped the air box holes to block them. Didn’t realize the effect was at high altitude.
Main jet at 125 and air fuel at 2 1/2 turns.
Went for a 80 mile trail ride. Much better riding. Still cuts out at WOT but I have a lot more throttle to play with before it cuts out. Plug looks good.
Valve clearances are within spec.
Considering buying a new snorkel.
After my ride, I decided I’d really like a rear disc brake! Also considering a 14T (15 T current) sprocket in the front for the trail riding I plan to do more. And a bit more of rise in the handlebar.
Any other suggestions greatly appreciated.
Thanks!

Glad it's running better. Get the DMO over-sized pegs. You'll wonder how you rode without them.

Second Peejman's DMO oversize foot pegs suggestion. One of the best add-ons you'll ever install on your bike. Don't leave home without them!..

Sales also help support this site. Yes excellent quality and service too. Buy with complete confidence.

Got the DMO pegs already after suggestions on this site. Agree! They are awesome!
Thanks for all the help.
Nate