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I think getting a real HP increase from one brand to another brand of filter element is:bs:. K & N s are okay because they are reuseable, but think about the physics here- More airflow by definition means a less-restriction (Read: not as good at filtering). Significant HP can be gained by changing the airbox design (eg. a CAI). Cold air is denser, and the design usually allows more air to be sucked in without a loss in filtration. But one brand's air filter vs another brands' in the same airbox assembly should not make much of a difference. More airflow = less filtration in that case. I wouldn't buy a K & N filter element just to put it in the stock airbox, especially since the original air filter is good for 40 or 50 K according to the owner's manual (unless you use your G6 for dirt-track racing...) I upgraded to a CAI on my V6 Probe, and I did notice a slight jump in HP.
But the biggest, cheapest HP gain I got bang for buck-wise was buying an aftermarket underdrive crankshaft pulley on eBay ($75) vs $350 for the stock replacement from the Ford stealer when mine needed replacement. I swear, that got me 10-15 HP easily, and I saved $275. The car had 100K on it when I did that mod, and it was stupid fast compared even to when the car was new.
Question: can an underdrive crankshaft pulley work on the OHV 3.9L, or does using an underdrive crankshaft pulley only work with OHC engines like on my Probe GT and the new 3.6L in the G6? I can't remember. The theory is that less mass/resistence on the smaller-diameter, lighter pulley allows the engine to rev with less resistence. The downside can be undercharging of the battery by the alternator and underperformance of other belt-driven components, although I didn't have any problems. Anyone know more about this?
 

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My advice really is to stick with a regular (cheap & durable) filter element unless changing the intake box entirely. And I have heard that people who overoil the K & N filters have reported lots of emissions problems, but if you follow the instructions, shouldn't be a problem. And don't get me wrong- I put a K & N element in the stock airbox of my '75 Porsche 914. It works fine, but I noticed no performance improvement. If I had it to do over, I'd just put a good quality (Purolator) air filter in (less than $10) and change it when it gets dirty with another $10 filter.
Re the underdrive pulley, I used one of bilett aluminum and it weighed half of what the stock one did, and spun faster because of the smaller diameter. Maybe I wasn't clear. Very much like unsprung weight on wheels, and how smaller-diameter, lighter wheels/tires result in an increase in quickness and a reduced top speed.
 

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I would watch the DIC for errors. If there is a big enough increase in airflow, I guess the emissions system could throw a code. Interfire suggested disconnecting the neg terminal on the battery if a malfunction presents, allowing the computer to recalibrate itself to the new, increased airflow which it will use to adjust the fuel delivery.
 

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Yeah, I'm sure the people who have problems overoil the filter. And if I remember correctly, there are really good instructions for applying the filter oil after cleaning it.
 

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Well, they do last forever. Post your impressions once you get it in :)
 

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I'm sure that you will be happy with the K & N. The one in my P914 works fine (and no ecu to worry about). Curious as to any performance gains- beware of the fresh oil change/car wash phenomenon where the owner senses his car is running better & stronger because he sunk some $$$ into his car. I swear my cars run better when they are cleaned and detailed, but I know it's just a subjective (and silly) case of wishful thinking. If you really notice a performance improvement, I'd definitely consider paying what you spent on your K & N filter.
 

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Just waiting for the results of your "Ass-Meter" test to see what you think when you get it installed... :)
 
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