interesting smoke stack?

[vaicase]

i have a 4 inch stack.no muffler.at the top i have a tractor flapper.at idle it is barely open.at full throttle it only opens up about half way.my qustion is am i choking my motor with this stack flap?i keep that flap so rain dont shoot all over the truck after setting.what do you think?thanks

 

[snow ram]

i have a 4 inch stack.no muffler.at the top i have a tractor flapper.at idle it is barely open.at full throttle it only opens up about half way.my qustion is am i choking my motor with this stack flap?i keep that flap so rain dont shoot all over the truck after setting.what do you think?thanks

do you think you can choke out that motor with a napkin?
that stack flapper , unless you put a ton of weight on the top of it, wont do a thing to hinder your performance