Ok then. To get power and speed from your 4.0, you are going to want to upgrade it to the 5.2!
I guess that doesn't qualify for cheap though....
What most people do is go to the K&N Fuel Injection Performance Kit (FIPK) first. However, that alone is not going to gain you much, so the next step is installing a header and 2.5 inch exhaust with high flow cat and flowmaster 70 muffler. Followed closely by a bored throttle body.
The mods you do not
The Tornado - or any other item that claims that swirling your intake air around will increase power.
the 1" spacer - this too is considered dubious. People that don't have it think they need it, people that have it aren't sure it is actually doing anything.