Just a curiosity, on the M8 header, where the left pipe enters, the pipe sticks inside a bit of the header. Why is this? Would it not flow a bit better being flush at the entrance?

 

i would figure to prevent or minimize crosstalk between the o2 sensors

 

I’m talking behind the cat, where the header opened to the muffler area. You can see it here in this screenshot of a YouTube video

 

Because it`s a tractor engine not an F-1 Ferrari

 

I expect the baffles in the mufflers slow things down a lot more than that.

 

It is easier to machine weld like that. If it makes you feel better, grind it out, but it won’t make a difference.