Dear Skirk;
Nothing runs well at +20F, Sir.
When there's frost on the outside
of the carb base It's on the inside,
as well. This is why V-8s have water
going through the intake manifold, by
the carb base. Inlines use the 'heat
riser', but most don't work well and
are removed as you have. Why many
had choke/throttle cables too.
The (5 min) 'warm up' is what you do,
during the winter months.
Headers will add some power after the
engine has reached 'operating tempature'.
Good luck.
