Problems at high speeds.

[unfazed]

It's a Motad stainless set with the link pipes between 1&2 and 3&4. I'd heard other types caused problems so made sure I got that spec.

I have the same down pipes on mine and it runs cleanly.
Did the issues come on suddenly or progressively?

Is the choke working correctly and the plungers seating properly when it is released.
This was the first thing I checked when it first happened on my sons bike because I had seen a similar problem on an old GS750 Suzuki when the plungers were not seating fully due to corrosion, a shot of WD40 sorted it out.
Have you checked all the usual items like wiring for corrosion.
Drain the float bowls to see if help first and then check the float heights using transparent fuel line.