Do any of you guys know what I can do with my 2003 Mazda 6 4 cylinder... I'm currently looking to beef it up a tad.. i wanted to start with K&N air filter... is this a good move?

 

cool air intake, exhaust, short throw shifter, those are kind of the basics. the next venture would be something like porting and polishing the head and intake manifold, header, coil packs, wires, upgraded spark plugs, voltage stabilizer, stiff motor mounts, shifter bushings, and so on. it is all about how much time and money that you want to put in.

 

what are u looking to "beef" up??
the looks or the performance??

the looks:
get some nice rims, like 17 or 18inch, with some low profile tires.
lower the car to reduce the wheel gap.
the end result looks killer.

the performance:
like wsoape said, start with a CAI intake, then a full exhaust, from the headers back.
this will make around 20-25hp. at least it will on the 3's.
personally, i'd be happy with that...
BUT, after that, id start with engine internals, and then eventually turbo it... now we're talking ALOT of horsepower..
but also do the electrical, like a standalone computer, upgrade the stock ignition stuff, then the motor mounts and a short shifter.....

 

oh, and to answer ur original question, a K&N filter isnt a bad start, but you might as well just get a full cold air intake. it will sound awesome (whoosh) when u accelerate, and will add a few horsepower