Jerry, I must respectfully disagree. While I have never used one on a 235, I did fabricate one to place on a 454 in a motorhome. There was a measurable difference in fuel economy (something like 6 percent). Not saying it would work in all cases, but it did on the motorhome.
I removed the original snorkel and cut a hole for a rectangular dryer vent hose to fit the air cleaner. I then cut a hole in the radiator support, and ran the dryer hose to the outside air. I then covered the hole with mesh to keep out the paper wasps and grasshoppers. More time-consuming than costly.
Jon.
