Oversized exhaust valves
well you've been exploring your options for 3 days.
Here's the summary.
Try to lap it in and if that doesn't fix it...
Replace the seat
Or
Buy the expensive 1.65" and hope like hell you don't have to replace the seat anyhow.
Or
spend a week trying to ****-hack it with whatever mismatched leftover parts you might have and hope like hell you don't have to replace the seat anyhow.