Did you jet up or down after taking the air cleaner off... without finding the A/F point that your engine likes for max power you didnt do anything but change the A/F ratio.. nothing is ever as easy as.. just do this or that and this occurs
I have a friend who runs the 14x3 with pleated filter top. Based on results I've seen posted here in the past I got him to make a pass without it. The car lost more than a tenth but the AFR leaned out 2 points and was dead flat instead of the wacky variations it normally has. He insisted in putting it back on instead of jetting up a little so the test was incomplete. I have no doubt that the air cleaner is restrictive on this '70 Swinger with 410ci smallblock and a 350+lb driver that was sooo close to that 10.0et he desperately wanted. It most likely would have cracked a 9 if I was driving it just due to the weight reduction. Logging AFR will show a restrictive air filter as richening at higher engine speeds.
