With the Delkevic headers or the ones I made?
The Delkevic appear to fit the pipes either side of the oil filter.
On my home made headers, I made No.2 pipe a slightly looser fit in the collector so two head clamp nuts removed and it will easily slide out of the exhaust leaving the rest attached to the bike. Not as good as being able to leave the exhaust alone with oil filter clearance, but I think the headers look better when all together but that's just me.
Replacing the pipe I use clear silicon sealant to stop annoying rattling of the pipe in the collector. I also use it to seal the pipes in the head, and no I didn't believe it would work when I first got told.