Now that you mentioned not being tuned on 98 and being at 0.30 gap. I agree that closing your spark plug gap is a good thing to do. You have further increased the demand on your current spark to combust your higher octane fuel.

Also 7173 coppers are NOT resistor plugs and can cause misfires, or interference with other electronics such as radar detectors, like in my experience. Get those NGK 2668's!

 

This is my problem 7500+rpm / light throttle, any ideas??

 

Likely in your tune.

 

what is your A/F like in that area? I had the same issue so I bumped my old thread up for you to help out.

 

You should ditch the 7173's. I switched to those from the iridium 8's a while back and had major misfire issues; switched back to the iridium 8's and it was gone. I'll never run another copper plug again; especially the 7173's.

 

you should look into kenne bell boost a spark

 

 

This may sound stupid, but I've experienced the same thing, but only when my fuel drops to 1/4 of a tank. I don't get that, I really don't...

 

Makes me think air might be getting in the line, idk.

 

That's happening because you are throwing all the fuel to the back of the tank when you take off if it's below a 1/4 tank and the pump is cavitating and pulling in air.