I few years ago I dyno'd a near to stock 440 magnum. I asked the guy what air filter assembly he was going to run. It was a restored 70' Cuda and he said he was going to run the stock dual snorkel. I made a pull with it in place and lost over 27hp. I flipped the air cleaner lid over like we all did when we were kids and then made another pull, gained back 26hp.Dave