Cheap Horsepower?

does anyone have a list of inexpensive things you can do to a fuel
injected engine to get small improvements in efficiency and power?
(Example: K&N filter etc...)
or any home 'remedies' to increase power or efficiency? (Example:
Wind screen behind throttle body to disperse airflow evenly)
i know i cant get any major power gain without spending some big bucks
but i'm just doing what i can until i can afford the more expensive
and effective upgrades.
thanks
almfreak