help w/ Exhaust leak/ "flat spot"

I have a c1 hybrid w/ a banshee motor and it has a serious exhaust leak between the headr and the pipe. I have tried everything I know to fix it and have failed. I'm about to just weld it. Please help me!
also, I have serious "flat spot" issues. From what I've heard, to fix the flat spot I need:
Coil,
Plug,
Reeds,
"reed block fix"
clutch springs,
Tachometer for setting the clutch.

any other mods? any suggestions on brands of parts?
Thanks!

For the exhaust leak you can use the silicone used as liquid gasket, it´ll seal nice