Siggy33 said:
So why do the K&N, MRT, and Air Aid kits not need a tune? They don't make the engine run "dangerously lean"? Are they more restrictive so as not to set off the MAF? If so, do they actually increase power at all? Basically are the kits going to make any difference?
I just don't get why Ford made it so that tuners would have to retune the entire ECU just for simple bolt-on mods....
The reason why those kits do not require a retune, is because the MAF housing is around the same size as stock.. and in some cases, such as the K&N, S&B and AFE kits. the MAF is actually smaller, in fact after speaking with tech's from both K&N and AFE.. I discovered that the MAF is 73mm. compared to the 79.5mm. stock housing, so the answer to your question is, NO.. they do not lean the engine out, and here's why.. Air travels across the sensor at the same speed and volume, because the MAF size remains either unchanged or is decreased, and despite the rest of the intake tube being larger in size, the computer still receives the same signal from the MAF sensor, indicating that air flow travel across the sensor remains normal and the computer therefore is able to compensate for the additional airflow, from the rest of the intake tube, because its within the 5%+ or - adjustment range.. So yes..they are restrictive, because the only way those kits are able to avoid setting off the MAF, is by decreasing the housing size.. So in reality, without a tune IMO.. you'll end up getting half the power, compared to kits that do require a tune, and to be honest with you..its really the tune that is going to provide the most benefits and gains, so in the long run..you would be much better off to invest in a tuner anyway..as for the MRT kit. thier website claims that no tune is required, However if you check out the cold score article, in 5.0 mustang and fast ford magazine 11 cold air kits were tested.. and included in that test was the MRT. according to the test results the MRT showed a 17hp. gain over stock. But on the other hand, the a/f numbers appeared to be around 13.1, which is considered to be lean.. And if you take a look for yourself.. the article does recommend a tune be required, in order to achive the best performance .. As for the Airaid kit. it doesn't require a tune, because it uses what is called a venturi tube, which is smaller piece of tube thats placed inside the MAF meter, which is designed to be similar to the stock housing, then if you should decide down the road to do any additional mods..the tube can be removed.. However once its removed.. a tune is then required, other than that..I really don't have any addtional info. so you may want to check out thier website, if you're interested in that particular kit. Anyway..I hope that I've been able to answer at least some of you're questions and have been somewhat, helpful.. just in case, I'll include the link for the cold score article, for you to check out.. And BTW.. good luck to you..
http://mustang50magazine.com/techarticles/m5lp_0601w_cold_air_intake/ 
