The problems you guys describe sound similar but Slingshot cutting out at highway speed is different. My only guess on that issue would be a loose ground.
Have ya'll checked the gap on your sparkplugs? The book recommends 0.9mm. The problems described, (accept for cutting out at highway speed), sounds similar to what mine did after I changed plugs the first time. I also got a check engine light. I thought I didn't connect something or I got a bad plug so I changed them again with 4 new plugs gapped at 0.9. Same problem. I measured the gap on my original plugs and they were about 0.75mm. So I did it again with 4 more plugs gapped at 0.8mm. The light went away after 3 heat cycles but I still had an issue with throttle response. I reasoned that the gap had opened up because of wear so I did 4 more plugs at 0.7mm. Problem solved.
If somebody told me this I would have my doubts but it really did happen to me. This all happened at about 20k and I have changed my plugs 3 times since then. Still using 0.7mm gap and going strong at 90k.
Last edited by jaknife; 04-16-2019 at 10:19 AM.