Your opinions wanted
 

Mainly for a possible chance of fuel economy gain, and then HP secondary, there are three mods that I get very mixed opinions on.

K&N air intake- I offroad, never through deep water, but what are the chances of sucking in alot of water when hitting a puddle or something?

Performance tuner such as Hypertech or JET- Premature breakdown of engine and possibility of not gaining much actual performance as the companies advertise?

Exhaust- more costly, but sounds good and also is cosmetically cool.

Which one could or will be more economic and throttle-responsive?
My budget is around 300.
Give me some pros/cons or personal experience. I have a 99 that has 31's and a brand new Jasper Built 4.3l with around 1,500 miles on it.
I get 15 mpg roughly.

ur best for the money is a good air filter and exhaust. the better the motor breathes the better overall economy and performance ul get. a k&n is a good air filter and as long as u dont put ur filter down in the motor compartment ul be fine and then go with a free flow cat and good flowing muffler. ul be surprised what those "lil" changes will make. and u should be able to get it all for under $300. and since u have the 4.3L go with a 50 series flowmaster for the muffler and u could also get a free flow cat from them. u could also size ur exhaust tubing up to 2" if u dont already have it, but it may be more money. good luck.