High RPM little problem..

Sounds like it starving for fuel at wide open throttle.
You could check what the float setting is, float should be level when up side down or close to that.
Make sure the fuel valve is all the way on.
Make sure the in tank fuel filter and if it has one, and if it has one, the fuel filter is not getting close to being plugged.
Check the fuel line make sure its not collapsed inside.
You could take the fuel line off at the carb let the fuel run into a glass bottle or jar see if your getting a good fuel flow how much should it? I'm not sure but you should get a small stream kind of like when you take a whizz only it won't be that fast?
NO SMOKING while doing this or NO open flame or HOT engine you don't want to go up in a ball of flames.
As for your jet size? I run a 0.65mm I'm 3400 feet above sea level. Some guys run 0.70mm that are close to sea level .
Those sizes are the metric drill bit sizes. You say you are running a #60 is that in metric? It maybe too small and causing the cutting out or surging at wide open.
You might want to go a little larger on the jet size. The main jet affects wide open so that may be whats wrong, if so it is a simple fix by going to a larger jet.
Norman
I'd try changing the jet all the rest is if you can't get it to work after changing to a larger jet.

I had this same problem, just above 30 the motor would start to vibrate badly and I'd lose power, even on a good downhill grade it would not brake 32 mph. I figured the problem was because the gas in the float bowl was foaming. I balanced my crank a bit and now it'll cruise along at 33 on flat ground no problem and even made it to 40 on a downhill grade.

With all the extras you added, did you replace the pixie straw clear kit gas line?
Get automotive fat gas line if not.
You might want to pull the tank and carb filters out too and just put a clear plastic filter in-line with the new gas line.

If you experience the problem again then look at it, if it has gas and no other filters in the way, the problem is elsewhere.

7300 is about grenade time for these little engines.

Just thought I might add that.

From assorted member's feedback, it seems that the "normal" redline for these engines is about 6000... granted there's a LOT of variance from engine to engine & you prolly lucked out and got one that's a lil better balanced than the others - but I figured I'd mention yer defo in the "red zone" lol

Still, I'd follow Norm's advice startin' with the float settings, I had a similar problem and that's all it was...

You have an exceptional engine if it will turn 8000 rpm.

By "grenade time" I meant most of them will start throwing parts at 7500 rpm if held there for a long period.

Save some for tomorrow!