Help Installing Powerbomb header

I just picked up a used Powerbomb header and I am not sure If I installed it right.
The stock header had a part that didn't fit with the powerbomb so I took it out, you can see it placed near the powerbomb header. Is this supposed to be installed with the powerbomb header? [image1]
Also, there is some spacing on the other end of the header once I've tightened it, is this normal? [image 2&3]
I just don't feel right with the installation.
Couldn't find a proper installation video.

You got it on there right.

The fmf head pipes are made to connect to the larger diameter pipe on the fmf muffler, when you use the stock muffler you have to leave the gasket out, its the only way to make it fit with the stock muffler.

The gap in pics 2 and 3 is normal, the stock pipe would've looked the same too.

Biglake wrote:

You got it on there right.

The fmf head pipes are made to connect to the larger diameter pipe on the fmf muffler, when you use the stock muffler you have to leave the gasket out, its the only way to make it fit with the stock muffler.

The gap in pics 2 and 3 is normal, the stock pipe would've looked the same too.  

Thank you for clarifying that.
Was a bit worried.

The installation guide on FMF site suggested I use "contact cleaner" & "high temp silicone", I didn't do either.
Should I take it out and do that? or is that not a big deal?

Also, I wasn't able to push the header in as much, probably because of the design/size of pipe/location.
I pushed it in as much as I can and tightened it.
what's the best way to check for leaks?

If its leaking any where you will get popping or backing firing when you let off the gas, if its not doing that don't mess with it and ride it.

Biglake wrote:

If its leaking any where you will get popping or backing firing when you let off the gas, if its not doing that don't mess with it and ride it.

If there is popping or backfiring on deceleration does it actually hurt performance?

TKO wrote:

Biglake wrote:

If its leaking any where you will get popping or backing firing when you let off the gas, if its not doing that don't mess with it and ride it.

If there is popping or backfiring on deceleration does it actually hurt performance?

Yes and no,

Decel popping doesn't directly harm anything. Most single cylinder, four stroke MX bikes have occasional decel popping that is completely normal.

However, the cause of the decal popping could. If it is a leak somewhere along the header/exhaust it is less of a concern compared to if it is because you are running a lean mixture...