What are the "holes" for on the downpipes?

[Tiggertoo]

So, I’m trying to track down the cause of misfiring/popping on the left cylinder. It happens at all rpms from 1,500 –3,000+ rpm on deceleration/closing the throttle. So far I’ve tried increasing the mixture which had little or no effect. Next I investigated the timing and thought I’d found the main culprits – timing was too advanced, a bad condensor, mismatched spark plugs and very old cables & coils. I’ve now replaced everything from the plugs to the points and set up the timing perfect. In fact it may be a degree or two retarded but it hasn’t made a noticeable difference.
Someone on here mentioned that it could be a leak on the exhaust side causing it, some youtube vid’s also confirmed this could be the cause. So I’ve checked the exhaust clamps and also the down pipe connections and that there are gaskets fitted in the head. Now I’m not an expert (this is my first Yamaha) but I’ve never seen any downpipes with holes beneath the flanges (3 on each pipe). Looking at genuine exhausts for sale on ebay they all seem to have them, though they are not shown in the parts manual.
Anyone know what they are for and do they go right through? Pics attached.
I’m now a bit flummoxed with the misfiring saga so have called it a night. I’ll probably investigate some other poss causes over the weekend but for now I give in. Suggestions welcome at this point!

 

[Tiggertoo]

Don't know why the images uploaded twice, it's just one of those nights LOL.

 

[Jim]

They're basically vent holes. The header pipes are double wall.... inner and outer. The holes just vent air between them.
In other words, not causing your problem.

 

[Tiggertoo]

Thanks Jim, makes perfect sense now. Told you its been one of those nights, my brain is not firing on all cylinders. Must be beer time LOL.