When i think to replace my air filter i saw on the market the square ones from bayless and others but didn't like it, I prefered to make my own style.

I got this on Pep Boys, a Edelbrook PRO-FLO, the filter element is easy to find and cheaper. To start I cut the base to make more shorter and fit under the hood, with a piece of carboard I made a circle from this base and then from my original air filter I made the webber base, with a steel sheet I follow my pattern and cut, align and welding both parts, install the rubber trim from the original air filter to attach carb and filter I made two holes and make with copper pipes adapters to let in 1.-breather exit from the engine plus air hose from the carb 2.-air pump intake air. I adapt the fresh air duct from the original filter, to avoid to stress the original hose, I found from 80's ford escort plastic hose and adapt to the air vent fan on the X1/9 and install the air hose.