I bought a 99 Blaster that was flat out abused. After working on this thing, pipe-k&n-sprockets. It was doing the same thing on top end power. I couldn't finger out the problem until I hit a water hole that went up to my jug. It sucked in water and after I replaced the base and head gasket, the pinging on the top end power was gone. Check this out! It's running ok at idle with your change of the main jet, but as soon as you crack the throttle it start to suck in air from the head some where. Good Luck.

 

I've tried both of those plugs and some #7 plugs to no avail it still runs like poop

 

Have you checked out your reeds? One could be worn or have a crack in it or something, worth checking out...

 

I have a twist throttle on mine. I also premix my oil. Runs great and has no rev limiter. I run it at like 16 to 1 or 20 to 1 just to be sure and I have had no problems at all. I used the have the problem when I had the stock throttle installed.