ORIGINAL: freakingfast
ORIGINAL: blw
You will make things a lot easier if you put an A3 plug in it. You have a great engine there that puts out a lot of power for the price. I wouldn't take 5 OS's for mine. You just need to get things right. The high speed was lean in the video. The low end sounded wet. See what the proper heat range plug gives you. The A3 is a game changer in the .455.
The muffler gasket will have no effect. You can run it without them if you want.
With the OS 8 plug, try easing the throttle up and down in increments so it has time to get rid of excess, unburned fuel.
Everything blw said. Yeah, loose the muffler gasket too, metal to metal is just fine.
Any muffler I connect metal to metal always comes loose. Tighten the screws when the engine is
hot, sometimes checking it 2-3 times after the engine has been hot and cooled, hot and cooled. Prevents the black/gray "goo" from getting all over and prevents muffler loss in the air.