Loss of power

[androu]

Hard to tell, really, it just doesn't have any grunt and gradually loses speed/rpm.

It does sound a lot like a fuel starvation issue.

When it slows does it feel like one cyl isn't firing or do both quit? If only one then I'd look at injectors. (it may not be obvious that it is a single cyl dropout with the muffler on the NT, have to carefully notice change in firing frequency).

I'd also not rule out a computer/sensor problem, even with no codes.

 

[androu]

Have done a couple more high speed runs with no issues. It's just hard to believe that plug caps would have caused the probelm. Wonder if I inadvertently fixed a loose connection or something while reachng in to replace the plug caps? Weird.

 

[dnktng]

Wonder if I inadvertently fixed a loose connection or something while reachng in to replace the plug caps? Weird.

The plug cap's connection may have been high resistance....simply twisting it may have fixed it but replacing the cap could not hurt anything.

How much disassembly did you do to replace the spark plug caps? Did you even lift the tank & disconnect the fuel pump connection? Access to the rear spark plug is a small PITA.