shandy294

My mileage has gone down(about 2mpg) except for one time it was about the same as before. Performance is better it seems (no proof). I think the decrease is mainly due to hitting it more but not sure. I haven't done any road trips and don't even have cruise control. 15.5 to 17.5 mpg range

QuietTahoe

If the air inlet doesn't seal out underhood air(and most don't), the PCM will start pulling timing out as inlet air temp increases. If I remember correctly, the PCM pulls out 8 or 9 degrees of timing as the inlet air temperature rises from 100F to 180F. My experience has shown the OE airbox to be best for cold air inlet on most trucks (and best fuel economy). As far as K&N and most similar airfilters go, they provide high airflow by providing poor filtration. They DO keep out large birds and low flying airplanes, but they are poor at particle filtration. Hold a K&N up to a light and look at the bottoms of the pleats. There is virtually no filter material at the bottom of the pleats and that is the direct route of the air. With tight piston to wall clearances and low tension ring packs on LS1's, I'll keep a good paper filter and sacrafice 1 or 2(at the most)HP and have my engine last a long time. That is especially true up north where there is lots of cinder and salt dust after the winter road work!